Does anyone know if there's a software around that could take an MP3/WAV and brake it inot the different channels, thus, isolate the vocal channel so it could then be remixed?
Such software does exist but the really goods ones are professional applications that you would have to shell out some good cash for. I'm not sure of any titles but look around and check out professional software companies.
Just search places such as Audiogalaxy for accapella's. I've managed to download over 200 good ones. Actually, just search "accapella" only, and see what the results are.