Don't forget the Dell L400. It might only be 700MHz, though (or was it 800MHz?). Still, if price is a major consideration, you might want to keep it in mind, as ye olde lappetoppes of yore at times command what seems like an equally anachronous price (i.e. high).
I just got a used C400 (P-IIIM 1.2GHz) and am pretty impressed so far.
EDIT: If you use a special "Visa 5% off" link from FW you can get an IBM Certified Used Thinkpad X22 for something like $607 no tax (I think), no shipping (I know for sure, unless the promotion expired), and a three-month warranty, extendable to 1 year.