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. This isn't a new search engine - it's been around for a good few months now and has been on my list to visit.
It works well - I tried it with a couple of unusual songs and it not only found them, but came up with good suggestions for other music in a similar vein. Worth taking a look at.