TTBO was my most successful personal project. It started by automatizing something I did whenever I discovered a new music band. First, check their top ten in last.fm (music charts service), then search those ten songs on Grooveshark (music streaming service).
I had the idea to get the top ten via API, and then embed a GS player automatically in a webpage. It started as a crude, plain HTML page and finally evolved to a complete website, with user registration (along with the possibility of selecting favorite artists and create playlists), statistics and a more pleasant design. Unfortunately GS was shut down on 2015 and TTBO had no purpose without their streaming service.
During its 3 years of life, it had 800k unique users, 2M sessions and 5M pageviews. It generated no income, but received enough donations to keep it alive. There's an archived, non-functional version, on The Wayback Machine.
This is the original sourcecode, made in CakePHP 2. It's horrible. I'm a better developer now. I think.