I’ve listed my Mac Pro for auction, and it can be found here, eBay item number 290375472021, entitled Mac Pro Quad Core 2.66 GHz / 7GB RAM / 640GB / eSATA. Bidding starts at $0.01, but if you are interested in buying it I’ll sell it outside of eBay for US$1800, payable via Google Checkout, PayPal, or cash.
UPDATE: The Mac Pro has now been sold. Thanks for the interest, everyone.