I have an old project (http://sudokugarden.de/ http://sudokugarden.de/) where I built a website about Sudoku back at University when I was bored. I consider it

I have an old project (http://sudokugarden.de/ http://sudokugarden.de/) where I built a website about Sudoku back at University when I was bored. I consider it feature complete, and have stopped to actively promote or develop it for two or three years now. I still make 1.5k to 2k per year in advertising (mostly CEO text links - adsense prices in that segement are too low to be profitable, and I don't want to bother the visitors too much. People who sign in for free don't see any adds). I made my first dollars a few month after the launch, when my adsense account finally reached the threshold for the first payment. I'm now working on a project where I want to collect semantic relations between books (sequels, prequels, translations into other languages etc.). It's not launched yet, so no income so far. It will have affiliate links to book stores. See https://github.com/moritz/quelology https://github.com/moritz/quelology if you are interested in details.