Ive been using this app for a while now and Im amazed that my kids havent gotten tired of it. They even ask me to put it on when they are going to brush their teeth or get ready for bed! It is deceptively simple, but it works.
Pro tip: the kids pretty quickly figure out how to run the app themselves, so I let them--they seem to enjoy it even more that way.
With the latest version, I like the ability to choose your own song from iTunes.
appluvin about Lickety Split