Girl Talk’s Feed the Animals is available as a “pay-what-you-like” system. You can stream the album on his myspace page (warning, his albums are labeled explicit).
I bought and loved the Night Ripper album because it is like musical trivia, trying to identify all the songs he samples. Then, I learned there was a wikipedia entry for that album (and this new one) so I can check myself. I am enjoying this new game of song identification and am happy to have something peppy for my workouts.