Vegetale hors d'oeuvres

Those little phyllo dough shells can be pre-baked (or make your own) and fill 1/2 of the shells with a roasted corn relish (corn, red bell pepper, cilantro, celery salt and lime zest) and fill the other half with a guacamole

I have this dish in mind. I am not sure what type of food you are planning on to cook for main course. But , I have this Indian dish to suggest. http://nyc.wholefoodsmarketcooking.com/recipes/11672_dahi_bhalla

You can make these in separate bowls also or on soup spoons. So , everyone can grab one and have it. The best part is it is served cold.

Spicy potatoes is also a good dish. Boil some potatoes , on a firm side. Add the dry spices like red chili powder, cumin-corriander powder, dry mango powder, garam masala , chaat masala. Take oil in a pan, add some asafoetida, cumin seeds, green chilies , curry leaves. Saute the potatoes , add salt, turmeric powder. Mix well and if u like caramelized potatoes cook it even little longer. Add lemon juice and cilantro. Arrange it on a platter with toothpicks or skewers.

A nice olive tapenade works for me. Make from scratch or buy a jar. Add some chopped sun dried tomato and a splash of balsamic for a different (and better) taste. Serve on crackers or crostini.

This mandarin orange brown rice salad is great and seasonal for the holidays. http://kitchenbelle.com/2011/11/03/brown-and-wild-rice-salad-with-mandarin-oranges-and-cooking-matters/
It's better the next day.
Use that to spoon into endive for a finger food.

Rice Stuffed grape leaves. (Dolmas) are good and can be made the night before.
http://www.marthastewart.com/353665/brown-rice-stuffed-grape-leaves
Omit the chicken broth and sub veggie stock.
You could also sub blanched cabbage leaves for the grape leaves.

Another one is simple lightly blanched whole green bean. (frozen small ones with the 'fancy tips' are probably better this time of year). You just want them lightly cooked and still crunchy as a finger food.
Warm a pan of olive oil with garlic and rosemary until the oil is seasoned. Remove the herbs and toss in the green beans with some sun dried tomatoes packed in oil chopped up.
Serve at room temp, toss with bread crumbs and parmigiana cheese before serving. Season with salt and pepper. Adjust salt depending on the saltiness of the cheese if using cheese.

Look at the entries for the current contest:
http://www.food52.com/contests/265_your_best_onebite_party_snack
lots of great ideas!