Music Smasher is a mash-up of popular music subscription service APIs. I developed it to simplify the task of searching across Spotify, Rdio, Grooveshark, and other catalogs to find out who has the music you love, giving you more information for choosing a streaming service.
Music Smasher is currently hosted at mattmontag.com/smasher.

Note that due to differences in the APIs, the result counts aren’t telling the whole truth (especially for Grooveshark). I hope I can fix that.
Please post any problems or suggestions in the comments.