Audiobaba Music Search is a next generation music search engine that allows you to find songs by acoustic similarity. Until now, there was no easy to way to browse for new music. Audiobaba lets you tell it what kind of music you like and returns results that sound like it but are in fact different.
I actually haven't checked this out too much yet, it is similar to Pandora (which you can't use in Canada anymore dammit!) Looks interesting !