Not as successful as the other ones here, but it's starting to show promise. http://mynativemap.com/

I created it to help people that can't surf into Google Map's in their own language. the link's forces the selected language manually and ignore the automatic language detection.

Started a few months ago and it's already covering my hosting in ad revenue. hopefully I'll have better numbers to report on the next Round of "...best passive income.." :)