Girl Talk is DJ/Producer Greg Gillis. What he does is splice and dice bits of dozens of different songs together to make songs. Not only do his creations sound amazing, but they are a music geeks dream because you can play guess all the songs that are sampled. You can download the new Girl Talk album Feed The Animals on his  website on a pay as much as you want basis like radiohead and NIN did recently here: http://74.124.198.47/illegal-art.net/__girl__talk___feed__the__anima.ls___/
If you just want to sample the sound go here: http://www.myspace.com/girltalk