In the wake of news that Virginia Tech would be migrating their Supercomputer Cluster from PowerMac G5s to Xserve G5s, the fate of the original PowerMacs remained in question. Srinidhi Varadarajan had said they were working on "very good homes" for the historic machines.
It appears MacMall is now selling refurbished PowerMac units from the cluster ($2799 each). Their promo page reads "Own a piece of history!".
Presumably this means that Virginia Tech has already started swapping out PowerMac G5s with the new Xserve G5s.
Note: Non "historic" PowerMac G5 2.0GHz (512MB RAM) refurbs can be found for $2399 at the online Apple Store.