We did this for our daughters (ages 6 and 8).  Their birthdays are only 8 days apart and the have a lot of common friends, so we did a joint party.  The theme was "Children of the World".   INIVITATIONS: We photocopied pictures of children from diffent counties from a coloring book we got from http://www.suttonfamilyfelt.com/social.htm called " Children of the World".  We put the party info. one one of the "Children of the World" figures, colored them and sent them to the children invited. We asked them to come dressed as a child from a country of their choice. Some of the countries represented were Germany, Japan, Russia, Armania, Mexico, and, of course, the USA.  DECORATIONS:  We used dolls the girls had from different counties and country flags (from a local travel store) lining the table. We also got travel posters from a travel agency and decorated the walls. We placed a big world map on the wall and had the kids put a little flag with their name on it on the country they represented.We found balloons that were multi-color swirled (green, red, yellow, blue)they were great because they seemed to blend the colors of many flags into one beautiful balloon. FOOD/CAKE: We had a little twist to the food served at the party. We asked each child to bring a treat from "thier" country.  We had a wonderful array of treats and the kids all got to try something new. For the cake, we just had a white sheet cake, with some fancy white edging and had "Happy Birthday Briana and Alyssa" in a different language.  We choose German. Then I bordered the cake with little paper flags from around the world. GAMES/ACTIVITES: For games I searched the internet for games from other countries. We found several relay, jump rope and group games from all over the world. We also had several crafts from different cultures for the kids to make.    TAKE HOME FAVORS: We gave the kids little goody bags filled with novelties from the Oriental Trading Company.   They have a line fo goodies that have pictures of children form around the world on them.  We gave a pencil, eraser, little bean bag ball, and stickers from this line. We also gave an inflatable ball with the map ofthe world on it and some candy. They also took home the crafts they made and got copies of the games we played.  We included a little information on the country and tradition behind each of the crafts and games. The kids had a great time and they learned a lot as well.  Many of the kids choose a country that was part of theeir ancestory and were able to share that with their friends.  We have moved and the kids have a new set of friends, and at 10 and 12, they want to do it again.