Here's a site that lets you add more cowbell to any song (MP3) you upload. I can't begin to count all the copyrights this thing violates, so you might want to act fast.
This is, of course, an homage to the beloved SNL skit featuring Christopher Walken.
I tried this last night and got a message explaining how the site was too busy to "render" my submitted song. (It promised to finish offline, but I never did hear the finished product). There are plenty of archived examples if you want to get the general idea.