Since I have a birthday in the winter (December) it is hard for me to come up with ideas for my parties. For my 13th birthday, I invited a bunch of my friends to play wally-ball. This is just like volleyball except that you play in a raquetball court. You can play off the walls, but only 3 hits are allowed per team. You can play with a regular volleyball or a walleyball, which is is softer. The facility you have the party in may have a walleyball, but if not a volleyball works just as well. After last year, I found it best to only invite five to eight people because the court becomes too crowded and it isn't as much fun. For cake, I had a chocolate/strawberry and cool whip cake. For goody bags, you can use anything you want. A good idea for only girls would be to put a small bottle of perfume and some candy and small make-up items in it, depending on the age. Have fun!