I've been playing with the iTunes Signature Maker, which is a scarily clever Java web-app that dives into your iTunes library and mixes a surreal 'signature' of the kinds of songs you listen to the most (or rate the highest). It pretty much sets itself up (I didn't even have to point it at my iTunes directory) but the output is highly configurable, letting you play around with options like number of tracks sampled and length of each sample. (Requirements: iTunes and a well-used library with play counts and/or ratings, and a Java VM -- runs inside IE or Firefox on Windows or OSX)
40 songs in 27 seconds, 627KB of mp3: my iTunes signature. My musical tastes definitely verge on the obscure so if my readership in its entirety (meaning all three of you) can identify more than about 5 tracks I'll be amazed (I know exactly what's in there and I can't make most of them out) -- consider that, if you wish, a challenge.
Here's mine, it's a bit unrepresentative as the program refused to use encrypted AACs.
But, it certainly shows the stuff I've been listening to lately.
http://works.music.columbia.edu/~jason/itsm/gallery/trj2.mp3