[Nilzor]

This is my portfolio :

http://www.nilsenlabs.com

None of them have made a lot of money, but one is still generating a small amount. Guess which. Hint: Income is not proportional with the shinyness of the technology stack

[daveguy]

Flags and capital quiz, 10k downloads. Little competition. I would say gogtasks for user need, but there's a lot of competition in that space.

[cmadan]

GogTasks? It seems to solve a real problem.

[OJFord]

I'd go with GetOut Ølbarometer - I think you're underestimating the European desire for cheap beer!