bacon wrapped anything -- potatoes, cream cheese stuffed dates, jalapeno chicken bites... they can be served at room temp, aren't messy, are easy to make, easy to transport, and are sooo good.

For Thanksgiving I'd prob'ly go with the dates, or maybe try bacon wrapped sweet potato bites, with a cheesy dipping sauce to go with.

oh -- and you can make them ahead. That's important too.

I'm taking the Pioneer Woman's brie stuffed mushrooms to my Mom's (45 minutes away). I'll prep them up to baking and then pop them in the oven at her house.

http://thepioneerwoman.com/cooking/2009/11/mushrooms-stuffed-with-brie/

Use leftover stuffing to stuff mushrooms!

I tend to bring dips (either ones that can be served at room temperature or only need a quick turn in the oven) and bring it in the dish I'd serve it in. I buy a high-quality loaf of bread and slice it into cubes. Travels well and not a lot of fuss.

Dips (Mexi dip is always popular, as are hummus, spinach and artichoke dip, and tzatziki), cheese and crackers, cut up vegetables (with one of those dips or homemade Ranch dressing).

One of my favorite snacks is hummus with sweets & beets chips by Terra chips. It looks elegant, tastes great, and seems a bit classier than your regular plain chips and onion dip.

do a blast from the past: clam dip w/ ruffles. no cooking & indulgent.

This is my go-to traveling appetizer... take a toothpick and skewer half a slice of english burp-less cucumber (bottom), a small cube of feta, half a cherry tomato and half a kalamata olive (top)... stand them upright on a tray and once you get there drizzle with a good greek or italian salad dressing. It's easy, pretty, you make it ahead and doesn't need to be cooked once you arrive... perfect!

Dips! A good bean dip with crudites and pita or bread. Or made-ahead tapenade, which keeps well at room temp with either some arugula thrown on top, or some feta sprinkled on top.

Nothing that needs to be reheated since the oven is a sacred, much-needed space on Thanksgiving day, and you don't want to be in the host/hostesses' way!

Edit: Even though you're not going on Thanksgiving, I still always try and bring apps that don't need to be reheated to the hosts' house as I don't want to be in their way in the oven/kitchen area.

thanks burrda2000, i'm making that as an accompaniment to my low brow clam dip.

These are all wonderful ideas to noodle on. Thank you for posting my comment and for all the great responses!

I took these vegetarian stuffed mushrooms to an Early Thanksgiving Party a few weeks ago. http://appetiteforconversation.blogspot.com/2009/11/ive-got-winner.html

I pre-made them, placed them on a baking sheet, and wrapped them with plastic wrap. Then I refrigerated them for a few hours. By the time I arrived at the party they were room temperature and ready to pop in the oven. If you use small mushrooms, they'll only take about 20 minutes.

It worked great!

I'm always at a loss in the same situation too. The appetizers I really love making and eating don't travel so well. They need last minute prep, oven time, or something else best done in my own kitchen.

So now, we go old-school classic: deviled eggs. They travel easily in one of those deviled egg rubbermaid containers and fit into a cooler for longer distances. And when we get to our destination, they get inhaled before we can even get them on a nice serving tray.

I'm going to start thinking about some other classics this year, like a cheese ball or pate/rillettes/terrine. And dips are a great idea. Silly that I never thought about them.

I tried the cheese straw recipe the other day, and they were just as good the second day as the first. I also tried the pesto and puff pastry palmieres, and they were good at room temp as well, though I thought they were best right after I made them. I added minced tomato and shredded mozzarella to them and rolled them up like a jelly roll.

An Italian appetizer might be a nice contrast to thanksgiving...
How about a caprese salad? Preslice and salt the tomato and mozzarella then drizzle olive oil on it when you arrive.
Or prosciutto melone?
Or if you have access to an Italian market you could do bresaola (dried cured beef from northern italy) garnished with arugula and shave parmesan.
All are a bit heartier than a salad but only need to be plated on arrival.

These antipasto skewers are my go-to and the first to go at any party:

http://theworldaccordingtoeggface.blogspot.com/2009/08/antipasto-skewers.html