Fastest "native" slot1 CPU is probably PIII 1000 MHz. It run at FSB 133. The board will work with it, but PCI and AGP are clocked at 44/88 MHz which is far from default.
Best CPU for this board is some tualatin celeron (with adapter). The board will run at 100 MHz FSB, which is officialy supported, so no problem should occur.
I also tried PIII-S 1400 MHz. It worked, but PC was not stable. Random restarts and lock-ups occured after some time. It didn't matter what I did (playing games, watching movies, running some stress program, ...) after some time (minutes to hours) freezed. It is strange, because PIII 1000 coppermine (with adapter) worked fine, so FSB 133 probably isn't the problem.
