I know they're a dime a dozen, but I grabbed up a 1.25GHz dual-processor Power Mac G4 on eBay. I had the single processor version released in 2003 that I use to bridge my old Macs with the new, but was eager for a bit more of the power that can be eked out of the dual-processor version that came out the year before. No hard drive, but I grabbed an IDE to SATA converter (which was cheaper than an IDE HDD) so I can throw an old 160GB SATA drive in there.