My boss at work just told me we’re going to be getting ten old Sun Rays that he found on eBay for something like $20 apiece. We’re going to put a Sunfire v20z behind them, probably running Xen. That’s a dual-Opteron beasty with 8GB of RAM. They’re fast, and they’ll be about a kajillion times better than my current 500MHz desktop. I’m really super excited about this.
Update 6 Apr: We got the Sunrays in today. They're exactly as awesome as I expected.