Something warm or cold with Spinach would be my first thought. If you can't make it ahead (to be warm) it doesn't take long to wilt or cook spinach.

Plus there are probably a million spinach sides out there.

http://www.wholeliving.com/photogallery/spinach-recipes#slide_1

Amber... I've been a convert to kale ever since my vegan/raw friend brought this massaged kale salad to dinner. She substituted dried cranberries and hazelnuts... wonderful! ... and colorful!

roast some broccoli, toss in a little lemon, kosher salt, pepper, garlic and even a little balsamic. can be served room temp.

there are a bunch of other room temp/cold roasted broccoli "salads" out there.

I second the call for salad. A nice Spring mix blend topped with Blue cheese, sliced apples and Pecans would be seasonally appropriate and easy as pie.

Hellooooooo brussels sprouts! I cut them in half and pan roast them over very high heat with a bit of olive oil. Add in a handful of chopped walnuts at the end and let the walnuts toast a few minutes. If you are going to reheat these in a microwave, toast the walnuts separately and add right before you serve. Microwaving the nuts can make them seem soggy.

Here is one for curried kale and potatoes and tahini: http://abcdsofcooking.blogspot.com/2009/07/potato-curry-with-kale-green-pepper-and.html

here is one for mustard greens and tofu:
http://abcdsofcooking.blogspot.com/2010/05/mustard-greens-and-tofu-curry.html

I am always the salad-bringer to our Thanksgiving dinners. Seems that meal standard is forgotten with all the oohing & ahhing over starches and sweets! Plus no laboring over a hot stove for that dish!

Here's another vote for salad! If the vegetarians are feeling awash in starches and aren't vegans, adding hardboiled egg for a hint of protein would be kind.

My childhood favorite is cheesy spinach; you could probably bring it warm and keep it covered with foil. It's quick and delicious.

Here is the recipe-- http://lauranav.com/2010/07/cheesy-spinach/

I don't make this head - but it's super easy and simple. Quickly steam Brussels sprouts, throw on some lemon zest, lemon juice, butter, seedless red grapes, and lemon pepper. Put the lid on the pan for 2 - 3 minutes so the heat from the sprouts warms the grapes (they seem to become plumper and juicier). This combo has color contrast, texture variation, and the lemon brightens it all.

Collard greens! We have them every year, and they can be done in a slow cooker and frozen ahead of time. They're also quite hearty, which is good if you're hosting vegans or vegetarians.

This savoy cabbage slaw with applesauce vinaigrette and mustard seeds is autumnal, can be made hours ahead as long as you keep the apples in acidulated water and add them at the end. It doesn't use any cream or mayonnaise. It's vegetarian and even fine for vegans if there are any at your table.

http://query.nytimes.com/gst/fullpage.html?res=9F06E1DA1230F93AA25752C1A96E9C8B63&sec=&spon=&pagewanted=all

There's an even better recipe for collards in the newest issue of vegetarian times, but how about this one from their website. I've had it before and it's pretty good!

http://www.vegetariantimes.com/recipes/11135?section=

brown a generous dollop of butter until it is fragrant, toss in a pile of thinly sliced brussels sprouts and saute until they turn bright green. can be served with sliced hazelnuts, but i found it unnecessary since the brown butter is so rich already.

also, you can remove stems from a bunch of kale, blanch it, chop, and serve with a homemade garlicky aioli. this dish gets better with time, so it's a good one to make ahead.

Simplistically - Peas.
I always think of adding peas to the family meals, more often than not meals tend to be brown (meat and potato people) And peas do not scare them off, as most things green seem to do.

They are also a nice addition to salads which also get my vote!

If not green salad, how about roasted broccoli with a vinaigrette? Or make a broccoli salad with raw chopped broccoli and vinaigrette. I think this recipe (http://www.nytimes.com/2008/02/20/dining/201arex.html) made without sesame oil and with lemon zest subbed in for the cumin would be great!

I really love this recipe for Citrus Collards with Raisins, and in fact when I tried it a few months ago I thought "this would be perfect for thanksgiving":
http://www.epicurious.com/recipes/food/views/Citrus-Collards-with-Raisins-Redux-352451

Thanks for the reminder, now I know what I'm bringing to the table this year!

In my opinion, astringent is the way to go for flavor. With so many starchy, savory, and sweet dishes around, something bright and tangy will be a welcome reprieve. I will, however, be a rare vote against a salad, because realistically diners will likely overlook the dish in favor of more indulgent options ('tis the season, after all).

A green side that's always a big hit with our dinner guests: braised asparagus. You can vary the recipe slightly to either be rich or (nearly) fat-free.

You'll need: olive oil, 1-2 bunches of asparagus (with tough ends removed), 3 or more sliced cloves of garlic, the juice of 1-2 lemons, and salt & pepper for seasoning.

Warm a large, non-reactive skillet over medium-high heat. Coat lightly with olive oil (or cover the bottom with oil for richer version). Add asparagus with the sliced garlic cloves and cook, stirring frequently until softened slightly. For lighter version, add a splash (1/8 c.) of water and cover tightly, steaming the asparagus for 4 minutes. Richer version, omit water and continue to sauté until softened to preference.

Now for flavoring-- whatever method used, once the asparagus is a little "al denté", add the lemon juice and season generously with salt and pepper. Cook, stirring frequently, until the lemon juice is reduced and clings to the asparagus. Serve hot or cold. Reheats well in the microwave or a skillet.

Bonus: The lemon juice will turn the asparagus tips bright magenta. Makes for a colorful presentation!

Wow, what great suggestions. I can't believe I didn't think of a salad. I'm going to run a few of these by the hostess and she what sounds best. Great, great ideas!

Just a plain steamed green veggie like broccoli, or asparagus, could be done in the microwave on the day of, and dressed up with some toasted almonds and a little browned butter made the day before.

Roasted brussel sprouts in balsamic vinegar were a surprise hit with the family last year...to the point where we had to make more.

Gotta agree with some other posters...I think old fashioned Southern collard greens would be perfect with all the comfort foods being served. Just sub vegetable broth for water and leave out the ham hocks.

I discovered a "mixed beans" recipe in an Irish cookbook a while back that was easy as pie, can easily be made vegetarian, and may be the perfect foil; I brought it to a pot luck dinner where a lot of other people had brought things like lasagna and baked ziti, so it was the only "plain green unadorned vegetable" foil for everything. The whole time I was there people were coming up to thank me for "bringing something that wasn't so rich".

And it was nothing more than a mix of steamed vegetables -- lima beans, green beans, butter beans, and peas were in the original recipe, and you can even use frozen. I couldn't find butter beans so I just used an extra bag each of limas and peas. Just cook 'em all up and toss 'em together in a bowl, then drizzle with melted butter. The original recipe also called for a little crumbled-up bacon on top, but I don't see why you couldn't just leave out the bacon and go with the butter alone. Or add an herb to the butter.

Yeah, it's almost a non-recipe, but I think the Zen simplicity is also part of the appeal.

Oooh! Just thought of a replacement for the bacon in my "mixed beans" recipe above --

Slivered almonds, toasted.

How about a no cream creamed spinach? This recipe uses white beans as the thickener and you can blend it until smooth or keep it chunky for a different texture: http://www.epicurious.com/recipes/food/views/Bean-creamed-Spinach-354031
I've made this many times, refrigerates wonderfully and can be spooned on rice, mashed potatoes etc. No cream in sight!

I've done brussels sprouts on the grill, they are wonderfully smokey and freeze well. Blanch them, drain them, and cook outside in a heavy skillet with butter, shallots, S&P. Bacon if you wish. Finish with a drizzle of balsamic and a handful of dried cranberries. The grill taste sends them over the moon, you can not get that inside. Make ahead and freeze flat, they thaw beautifully overnight in the fridge and can be eaten at room temp or gently warmed in the oven.

I agree with EVERYONE who has said Kale. Even something as simple as kale chips can work and our delish.

i made this spinach dish last thanksgiving and it was a big hit.

http://www.marthastewart.com/portal/site/mslo/menuitem.fc77a0dbc44dd1611e3bf410b5900aa0/?vgnextoid=2b5b3e8661aa5110VgnVCM1000003d370a0aRCRD&vgnextfmt=default&backto=true&backtourl=/photogallery/thanksgiving-sides#slide_10

Here's two that I've made with success:
http://theexperimentalgourmand.blogspot.com/2010/01/spiced-pecan-and-pear-salad.html
http://theexperimentalgourmand.blogspot.com/2008/11/potluck-standby.html

Also, what about green beans almondine? The way my mom made it was straightforward with beans, toasted almonds, a bit of butter. Got us kids to eat our greens on Thanksgiving and Christmas (the only two times in the year that we'd have it).

Last year for Christmas we made Nigella's Christmas salad (recipe here but instead of the chicory and radicchio, we substituted green lettuce and maybe some of the radicchio. It was delicious, the pomegranate seeds make it suitably festive and the dressing was great.

Also, I second burrda2000 about the massaged kale salad. Use massaged kale instead of lettuce in most salads, I find it goes really well with dried cranberries, sunflower seeds, goat cheese and a simple vinaigrette dressing. But it would be nice with pomegranate seeds and the dressing from Nigella's salad too!

Salads are definitely the way to go, though. I always welcome a tasty one after a huge meal.

I'd do a salad as well. Our house salad is whatever greens looks good, a balsamic vinaigrette with blue cheese, and toasted pecans and dried cranberries. Ina Garten also has a Cape Cod Chopped Salad that is very festive looking and quite yummy.

Greens are a great Tday side dish. I have a slow cooker recipe that has a few Asian flavors on my blog if you're interested: http://healthyslowcooking.wordpress.com/2010/02/02/slow-cooker-asian-greens/

I love to make side dishes in the slow cooker.

I am so surprised only one person said collard greens. A table without them at thanksgiving is not complete (braise your smoked turkey for stock - add salt, pepper, a little garlic and as they get tender, add sugar to cut the bitterness). I have been advised not to show up at our company holiday party next week without them!

I love lightly boiled fresh green beans with a dijon mustard vinaigrette.

Also, I'm surprised no one said this (maybe it's too starchy for some) but lightly boiled green or savoy cabbage (or both!) tossed with a little butter, salt, and pepper is lovely and green-tasting. And more in season than fresh green beans. And way cheaper.

I have been asked to bring a similar dish and will be going with kale salad thinly sliced and tossed with pecans, cranberries, feta cheese tossed with a lemony vinaigrette.

Brussels Sprouts - put them in a food processor with the slicing attachment and slice into rounds (they will end up like a slaw). Caramelize over high heat with a little olive oil until almost burnt. It reheats wonderfully and can be dressed up with toasted pine nuts or a drizzle of balsamic syrup... but I love it plain. It goes so well with turkey.

I make this every single year because people who've eaten it ask me to make it again! Super simple, really tasty:

http://www.epicurious.com/recipes/food/views/Green-Beans-with-Pecans-Lemon-and-Parsley-102500

Green beans topped with slivered almonds and a dash of butter - can be par boiled and then heated through in microwave

Or peas - with loads of mint and a pinch of salt. The mint adds a bit of freshness amongst the gravy and creamy, cheese toppings.

We love, love, LOVE Laurie Colwin's creamed spinach with jalapenos. It does have a slight gooey/creamy factor, but the heat factor adds much welcomed zing to the Thanksgiving table.

https://mywebspace.wisc.edu/dsshapiro/web/recipes/colwinspinach.html

Our new favorite thing is swiss chard sauteed with garlic, pesto (homemade or bought) and diced red peppers. It takes about 5 minutes and tastes wonderful and healthy!

Heck yeah! I'm making Collards with raisins in an orange reduction. I got the recipe from The Splendid Table and it's always a hit. Plus it costs maybe $1 to make!!!
http://splendidtable.publicradio.org/recipes/sides_citrus_collards.shtml

Kale salad is always good - especially with a spicy peanut dressing. If you want to make something hot, roasted broccoli and grilled asparagus (use a grill pan if you don't have a barbecue) can be reheated in a microwave.

I'm a little late to the game, but I 2nd or 3rd the collards with raisins in orange reduction. AMAZING!!

Sliced cucumbers in a water/vinegar/oil bath.

I think this is a european recipie its something my grandmother makes.
roughly peel lebanese cucumbers
Fill a bowl with white vinegar, salt, pepper, a dash of oil and water (to your taste, it should be very light and refreshing, not strong)
thinly (use a mandolin slicer) slice the cucumber into the bowl.

The bowl should be deep and the cucumber should sit ontop of all the water.

Its one of my favourite things to eat after a very heavy meat-based christmas meal.

On Mark Bittman's make-head recipe list for Thanksgiving, there's a brussel sprout salad - chop up/process raw brussel sprouts so they're shredded, toss them with his lemon vinaigrette and crumbled cooked bacon, and serve. I made it last year and the family's requested it for this year.