One of the first sites I ever found that did interesting audio collage work was bits & pieces, a project put together way back in 1999 (and still going strong) by one peter m traub as part of his studies at Dartmouth. The bits & pieces site consists of programs that automatically trawl the Web for audio files and throw together randomized mixes of those sounds based on a few general remixing templates. You're not gonna get a Jason Forrest album*, but if you have a listen long enough you will hear some fascinating remixes, somewhat reminiscent of number shortwave radio stations. I fondly recall hearing one mix long ago that juxtaposed the Scooby Doo theme song with Charlton Heston's line from Planet of the Apes: "Get your filthy paws off me, you damn dirty apes!"
* Well, not unless someone wants to make bits & pieces v2.0.