I'd get a VIA Apollo Pro 133A-based motherboard and maybe pair it with a nice Matrox AGP card. It depends on what you already have, really. I tend to go with different types of hardware in different builds because I like diversity, e.g. have one build with a Voodoo, then one with something from S3, another with a Matrox and so on. I think there is no need to go beyond DX7 cards with a P3-866 unless you have a few to spare, so something like a cheap and plentiful GeForce MX440 would also fit nicely. Oh, and a tip for nVidia cards: always look into the equivalent Quadro card. Sometimes you can find the Quadro cards cheaper, and they are guaranteed to have a decent build quality.

You can get an Intel 815-based motherboard as well if you don't mind losing the ISA slot. I'd avoid the 440BX because I'm against OCing retro-hardware, and using a 440BX with 133MHz FSB clock would OC the AGP bus.