I read about this in Electronic Musician magazine. It's called www.nowrecording.com. "Members" can post mp3s and have other musicians "audition" to play parts ... just d/l the mp3, convert to your favorite recording format, lay down your track, save to mp3 and upload. Fees allow for private projects -- you and people you know can share files online, and not just mp3's, but .wav. I haven't signed up yet, but the fees don't look to prohibitively expensive. Anyway, thought I'd share it with a few folks.