Hey Camn, how's things in Seattle?
Well I am sitting at work right now reading the Mobo manual for the P2B-f (manual revision 1.03). Since until recently we have bought all ASUS boards I have quite the little pile of ASUS manuals. As you probably already know the fastest CPU listed for your mobo is a PIII 550, 100 bus. However, since the board supports a bus multiplier up to 8X, it SHOULD support up to a 800 mhz processor with no issues.
There is an option to kick up the CPU bus frequency to 133, which means you could theoreticly run a 1 G PIII, but the 440BX chipset isn't designed to run over 100 bus speed.
Any P3 chip you will find now will be a socket chip (flip-chip) so you will need a flip-chip to Socket A adaptor. I'm using one in a later model ASUS board and it works fine. If it were me, I would go out and get a P3 933 chip, they are good "bang-per-buck" among P3's right now. It will be capable of 133 bus speed even if your board is not. Start it out at 800, if all works well you can play with it and see how far you can push it. If the board gaks, you can then decide to either throttle back or pick up a newer board.
Let me know if you need the mobo jumper settings.
RW