SKYBASE Although it lacks in a couple features which would have made the software more useful, I think it's the sort of thing I was looking for. It isn't really a tool for finding loops in music or anything else, but its rather for finding loops in sampled material. For example, I sample a hardware synthesizer, and then I look for sustain loops using the program, and finally I can import the looping sound into other samplers.
This is more for developers of musical instruments than of general use.
(Version 1.0rc2)