There's a Centris 660AV in great working and cosmetic condition on Craigslist. It's in Denver, and it needs to be rescued by Wednesday or it will be recycled. I know the Quadra 840AV gets all the glory, but the Centris 660AV, which was released in tandem with the Quadra, also has some historical significance -- and it's fun to play with too. The Centris badge is relatively rare, since Apple changed the model name to Quadra after just a few months.
Here's the link to the CL ad: http://denver.craigslist.org/sys/4509477916.html
(Note: This is not my listing, so please don't reply to me! I'm just posting it here because I noticed the ad and hope someone can get this machine before it's recycled.)
Here's one of the photos: