I made FiveStar [0], which was covered on TechCrunch [1] and it made ~$600 last month. Doesn't cost any money to run, so it just sits there. Not a fabulous success story, and traffic is decreasing, but $10 a day as passive income isn't awful.

[0] http://fivestar.io [1] http://techcrunch.com/2014/06/03/fivestar-finds-the-best-pro...