Remember Hobnox Audiotool, the flash-based app that runs in your web browser? The good news is that this has now been turned into an Android app, so music makers who've been relatively starved of such things on Google's mobile OS now have another option.
Audiotool Sketch gives you two drum machines and a bassline synth to work with, all of which enable you to create patterns. It's currently available on the Android Market for £0.99, but this is an introductory price so grab it quickly if you're interested.