Reader Marlow77 has put together a set of instructions and custom scripts to build your own instruments for both BeatMaker 2 and Thumbjam. This is awesome! If you've ever wanted to take the sounds you're generating with a computer-based VST and bring them over into your iPad, he has the solution!
These instructions will only work in Windows, but some time in the near future he plans to mass produce a bunch of new instruments for both that will be available for download on his site.
All of this is freely available, but Marlow77 has a donation button at the bottom of the page. He notes that the proceeds from donations will go directly to developers... because he's going to buy more apps!