Depending on your crowd (foodie or not) a mexican or greek layered dip can be a great option. There are multiple recipes on the web for either of these, and you can easily jazz them up with hardcore homemade ingredients or make them ridiculously easy with store bought ingredients (again, depending on you and your crowd).
I do this all the time for all different types of audiences, and they always fly off the plate. I toast pita for greek or buy fresh tortilla chips (or make my own) for the Mexican.

How about cherry tomato, mozzarella, and basil leaves skewered on toothpicks? You could drizzle the plate with olive oil and balsamic too if you wanted. Tasty, no need to keep warm, and the colors are festive!

This year I'm making the Zucchini Ricotta Cheesecake from 101 Cookbooks. She recommends serving it room temperature, which I can say from experience is delicious. It's also a very pretty dish, which is always nice. You can vary the seasoning to suit your host's meal if you want. I did fresh oregano in the summer simply because I had it. on hand.

http://www.101cookbooks.com/archives/zucchini-ricotta-cheesecake-recipe.html

That ricotta cheesecake looks amazing, I bookmarked that for sure.

I made Smitten Kitchen's Stuffed Mushrooms and traveled a few miles with them for Thanksgiving; they were a hit.

http://smittenkitchen.com/2006/11/grievances-aired-caps-stuffed/

Lentil salads with vinaigrette, and topped with feta, are great as side dishes and can be served warm or at room temperature. Grain salad with farro, barley, wild rice and any assortment of vegetables are good. Potato gratins can be made ahead of time and brought in the baking dish and warmed in the oven before serving.

I'm bringing a 'green vegetable' for a holiday dinner in a few weeks, and found a green bean dish that can be served at room temp:

http://www.realsimple.com/food-recipes/browse-all-recipes/green-bean-salad-walnuts-fennel-goat-cheese-10000001031592/

If you'd like to have the green beans be warm, you could keep them separate from the rest of the salad, microwave them for about 2 minutes just prior to serving, and then toss everything together before you put it ion the table.
Just another fun option!

Oh - also - Donna Hay makes a yummy asparagus ricotta tart that would be great at room temperature, too:
http://www.donnahay.com.au/menus/outdoor-favourites/springs-bounty/asparagus-and-ricotta-tarts

I have a killer Mediterranean bean salad that is served cold so it travels like a dream. Chick peas, pine nuts, split peas, onion, cucumber, tomato, feta cheese, a couple types of olives, and some cilantro all chopped and mixed together with a basic dressing of lemon juice and oil with salt, pepper and oregano. The amounts are all adjustable to what you like, and it's really easy to change up based on what you have. Avocado or artichoke hearts are good in it also. Leave it sit in the fridge overnight and it's amazing the next day.

You guys have great ideas, much more diverse than I expected! Thank you!!!

I made this for Thanksgiving dinner and several times since - they are great room temp and seriously, the brussel sprouts take less than 5 minutes in the pan.

http://www.latimes.com/features/food/la-fo-calcookrec23a-2009dec23,0,6215694.story

I made marinated mushrooms for a party this week and they were a hit. They are meant to be served at room temperature. Basically you make a vinaigrette bring it to a boil and add the mushrooms. Turn the heat to low and cook, stirring occasionally for about 8 minutes. Allow to cool for a bit and pop in the fridge for 24 hours. Yum.

Another thought, how about a waldorf salad? I make mine with a couple different kinds of apples, some dried cranberries and raisins, some toasted pecans, and a dressing made from vanilla yogurt with a pinch of salt, a touch of brown sugar, and a little nutmeg. You could bring the fruit pre-chopped with a little lemon juice sprinkled on it, and the nuts toasted separately, assemble the salad on site.

A winter fruit salad with grapefruits, oranges and pomegranates could be lovely with a sprinkle of Grand Marnier and a touch of sugar.

I know you said no salads, but my stepmom has a recipe for a wonderful pomegranate salad that I think you could still serve along with a more traditional salad.

It's pretty easy and can be served cold and it's super festive-looking. I posted the recipe here.

try yotam ottolenghi, most oft his stuff can be served at room temperature:
http://www.guardian.co.uk/profile/yotamottolenghi
Everything I tried was really outstanding. I did the fried cauliflower and served it room temperature: http://www.guardian.co.uk/lifeandstyle/2010/jul/17/fried-cauliflower-tahini-recipe-ottolenghi
If you get artichokes, try this dish:
http://www.guardian.co.uk/lifeandstyle/2010/jun/19/globe-artichoke-mozzarella-salad-recipe
For a more filling side I would do: http://www.guardian.co.uk/lifeandstyle/2010/jun/12/chermoula-aubergine-bulgar-recipe-ottolenghi