The Prosper Days 2008, next week Monday and Tuesday in San Francisco, are the main yearly event by Prosper.com. The schedule covers topics like borrower experiences, managing large portfolios, earning a risk adjusted return, collections. You can still register for 55 US$ (includes all sessions and meals).
Several blogs already speculate if and which new features will be announced at the Prosper Days 2008. Traveler wrote a long post on that yesterday.