I recently start creating android application because I like the mix of graphics and programming a lot.
Currently I've got 2 application published on the Android Market:
Q&A for professional and enthusiast programmers
Q&A for people studying math at any level and professionals in related fields
Q&A for pro webmasters
Q&A for professional, enthusiast and amateur photographers
Q&A for electronics and electrical engineering professionals, students, and enthusiasts
Q&A for Ubuntu users and developers