Instantly play any song on the web, without even knowing its name!
This little app is pretty neat. Finds songs by name or by lyrics, plays them in the browser. It sources them from youtube. Only ever had an issue with one so far – The Rolling Stones – Sympathy for the Devil, which was set not to be embeddable.
UPDATE on Monday, February 1, 2016:
Anysong.io seems to have been taken down, presumably it angered the gods of music law. However, the source is still available on github if anyone is interested.