My first one (not being used right now) is a P2 MMX running (overclocked) at 250MHz with 192MB RAM. Just can't get the USB port to work with an external USB modem.
Borrowed a machine from a friend that's a 600MHz P3 Celeron with 128MB RAM.
I'm now thinking of getting a better machine.
Something like a P4, 2.8GHz, 512MB DDRAM, ...
Send in suggestions if you have any on what I should be getting, even in terms of recommendations on Motherboards, accessories, etc.