That could be any number of boards, so many that for a good recommendation you'd better give some more requirements:
- is AGP required, or is onboard/integrated VGA good enough?
- if AGP is required, which version? (1.0/2x or 2.0/4x)
- how many PCI slots
- how many DIMM slots (and how much memory in total) required
- form factor (AT, ATX, uATX etc)
My general test board would fit your requirements - it's a Tyan Trinity 400:
- ATX
- Via 694X (ApolloPro133a) + 596B chipset
- Slot 1 and So370 FC-PGA
- 3x SDR-SDRAM DIMM slots supporting 256Mb chips, so max 512MB per DIMM, 1.5GB total
- AGP 2.0 (4x)
- 6x PCI
- ix ISA
- PATA-66
Would I recommend it? Depends. Despite a plethora of options, I find the BIOS rather unstable. frequently requiring an ESCD or even CMOS reset after changing hardware (particularly ISA hardware). Also boot is relatively slow. For testing purposes the slot+socket are great (as is the ability to boot from any kind of ATAPI device or any of the attached HDDs), but pointless for a steady config. I'd probably suggest something like an Asus P3V4X - but tbh, just roll with whatever you find: if your demands don't go further than a slot 1, 133MHz FSB and ISA there's tons more out there that would work fine.