drumbit - A very easy to use drum machine.
Type Drummer - Drum by typing
Sampulator - Make (and record) beats on your keyboard
MixPads 2 - MixPads 2 is an elegant mobile app that works as a music creator and helps you to access musical communities on social platforms.
Djay - djay gives you instant access to all your existing tracks and playlists from iTunes.
Splice Beat Maker - Make and share beats in your browser