music, cool clothes, or you could save it for something big. Go shopping at your fave stores and if you see something you like, go for it. Your mom probably wants you to spend it on your birthday.
Hold onto it until something really cool is out and you want it. You don't want to look back and say "Wow, I had 55 dollars, I could've used it on that"
CD's or iTunes. When you find a song that has a good beat and good sound, there's nothing better than that. I reccomend Panic at the Disco and My Chemical Romance.
Get a DSi XL! It's a DSi but it's BIG! Or for DS, a game called Scribble Knots! You can write in anything (some stuff won't work)and it comes up on the screen! You play as a boy named Maxwell, and he can kill the things you make! It's so fun! Oh, and Happy Birthday!That's a pic of a cute seal on its back! LOL so cute!
I don't know your preferences, but I know I'd buy manga. I love me some good manga. I'd probably get some One Piece, Ouran High School Host Club, DNAngel, InuYasha, and Naruto. Then I'd only have 5 bucks left, but I would be very satisfied with my new purchases.
(I recommend getting your TokyoPop favorites before it closes it's American branch. Just sayin'.)