The University of Arizona holds auctions to dispose of "surplus property". At the present time, the auctions are held every two weeks, and are live auctions with an auctioneer and the whole nine yards (they used to be sealed bid sales -- I'm not sure which I prefer as a prospective buyer).
Visit their website which has schedules, results of past auctions, and more.
Policies change all the time. You used to have to register in advance to get a bidder number. This no longer seems to be the case.
Tom's Info / email@example.com