JavaRosa is an open-source platform for data collection on mobile devices. Basically, a supped-up XForms browser for Java ME, it's pretty awesome.
- Open Data Kit
Built on JavaRosa, it's designed specifically for Android, and to take advantage of all the awesomeness that is an Android phone.
I've decided in the coming weeks to play with ODK and blog about it, and try to think about other solutions for mobile offline/online data collection. I haven't done mobile development before, so this will be interesting.