If you've not checked out new york based, www.ArtCycle.com, you should.

It's a new curated website (aka.. a contemporary art pawn/consignement shop), and like Artnet.com it also is helping give the much needed liquidity and transparency to the contemporary art market.

They only started up in November 2008, and they actually have an impressive list of Contemporary Art inventory already.  They already have works by some impressive artists : Araki, Eggleston, Oliver Boberg, Hirst,Candida Hofer, William Kentridge, Opie, Anselm Reyle, Lisa Ruyter, Andrees Serrano, and Kehinde Wiley just to name a few.