EcoQube Aquarium - Desktop Betta Fish Tank
This is my favorite so far, it comes with a complete starter set so you don't need to buy anything else (except for the fishies!)
This one get's the highest reviews of all of the small fishtanks I researched. It includes an MP3 player with "nature sounds". That sounds a little weird to me and the look isn't quite as cool in my eye so I probably wont be getting this one, just wanted to share as everyone seems to love it.