I pissed off Ray by mentioning this on one of the AInc. lists a long time back... It's still the only 'normal' place I've seen loose PowerPCs sold, and apparently my enthusiasm made me sound like a spammer.
Anyhow, here's
the product page on PCSurplusOnline. Only 166MHz, but seemed like that's good enough for accellerator repair or somesuch thing. 60 left in stock, they waive shipping on orders over $100?, and usually have N% off deals going if you opt-in to their announcements.
(I've got to mention the shipping/discount BS, as their prices on normal stuff seem a little otherwise-inflated to compensate, and otherwise people think I'm nuts for mentioning them as an alternative to, say,
CompGeeks.
The big advantage for me is that they're on the east coast, which is a godsend when you need to replace someone's Packard Bell with something marginally standard on the cheap, and don't want to wait the week and a half for shipping from California... Those on this side of the US might understand my enthusiasm, while you lucky left-coasters with easy access to Fry's and used shops that don't ask $500 for Pentium MMX-era machines are free to think I'm a company-pimping bastard. ;-))
Edit: Yikes, T-Bone beat me to it, and I need to remember to read the whole thread before posting... Okay, then maybe the discount BS is a worthwhile headsup.

FWIW, N is usually a value from 5 to 25, varying by week.