Have you ever done a party where you ask the guests to bring themed food. Such as Italian night or mexican?

I have! It's fun. Usually we would do it with an e-mail invite. In my experience, the best thing to do is give some guidelines. Suggest everyone bring enough food for x number of people to have a little. Then, include a link to a couple websites with recipes. You might want to ask people to e-mail you to tell you what they want to make so you don't have 10 people bring tzatziki and pita to a Greek night or something:)

We've done lots of Italian, Greek, south of the border nights (anything Mexican, Central American, South American), Middle Eastern, Japanese, and Caribbean (including Puerto Rican/Cuban).

Some examples:

Italian: Bocconcini, Caprese, or Bread/Panzanella Salad; Broccoli Rabe/Rapini and White Beans; Baked Pasta or Lasagna, non-baked pasta... maybe penne all'arrabiata, etc; Some guests bring wine; Tiramisu or Cannoli, etc., etc.

Greek: Pita, dips (Tzatziki, Skordalia, etc), Dolmas/Stuffed Grape Leaves; A big greek salad (sometimes traditional without any lettuce, but sometimes people have used romaine or spinach which is delicious as well); Vegetarian Moussaka; etc etc

On South of the border nights, usually we bring components for one dish: Guacamole, Salsa Verde, Sour cream, Beer, Some other salsa (regular old red salsa, or something interesting), Avocado/Hearts of Palm Salad with oranges, cilantro, romaine, and a lime dressing (I think this is roughly based off a recipe from a friend's Brazilian husband), Rice and beans, tortillas, Churros, etc. Sometimes people have brought traditional things like tamales, too.

If you're playing poker, you might want to make sure things aren't too messy!

Great idea and great tradition. I have done something similar. My most popular one is my Chili Night. It works very well for poker. Any leftover chili can be frozen for a future dinner.

I usually make a couple of different kinds of chili (you can do it a couple of days ahead) and then have everyone bring either side dishes or toppings. I got the idea from

http://www.chili-everyway.com/side-dishes.html

I send them to the website with instructions on what dish to make

it is fun and very popular.

Sometime if I am very busy I have people make one of the chilies.

Yes, we had a "NY" themed party last year. Our friends brought things like NY-style pizza, chicken wings and chicken wing dip, stromboli, NY cheesecake, and we served Zweigle's hot dogs - they are from our hometown upstate.

We also sometimes have a Hawaiian Luau themed party where we had Hawaiian chicken, tropical fruit salad, mai tais we drank out of coconuts and other things. It was fun to dress up to that one!

We did luau and had a do it yourself shish ke bob bar. Had fruity drinks and had all bring an exotic dessert.