If you're not looking for a homerun, I suggest you look at niche markets.

I'm making about 15k/yr w/ my niche product: http://createyourproglang.com/. Where I live it's not enought to replace my job, but it's a nice complementary income.

There was a nice thread recently on HN about ways to find & test a niche market: http://news.ycombinator.com/item?id=1454221