You won't find a shortage of playlist generators out there, but Boil the Frog does things a little differently. Instead of simply asking you to pick an artist or two to generate a playlist, Boil the Frog has you pick two and then bridges the gap between them with 13 other songs.
The whole thing works like a "six degrees of separation" game. Start by picking two artists, and then Boil the Frog generates a 15-song playlist that leads you as logically as possible between them. When it's done, you can either listen to quick 30 second samples of each song, or important the playlist directly into Rdio. If you're struggling to figure out what to listen to, but have a general idea of a tone you want to go for (Black Sabbath to Carly Rae Jepson), then Boil the Frog is a fun way to do it.