I have built many systems with intel CPU's on almost all chipsets (BX, Apollo pro 133a, 810, 815). I currently have a MSI 810 board for a 2nd system & it overclocks great -- but it is not a good performer since it is after all a 810 board. I do not like the 815 boards. THe VIA boards beat them in price per performance. THe VIA boards are usually @ $100, while the 815 boards are usually around $150 (for quality boards). They perform almost identical. The 815 board gets a few extra 3d marks & FPS's, but is limited to only 2 RAM banks that can be used at 133mhz. I'll take a quality Asus, Abit, or MSI VIA apollo pro 133a board over any 815 board. If you want to overclock celerons, BX is the way to go. But with BX, you need to get a controller card (unless you want to be stuck with ata-33) & they do not have the proper agp ratio's for 133+ mhz (not good for overclocking PIII's).
I'd have to rank the Abit VH6 II as the best overclocking board for PIII's. It is a apollo pro 133a chipset, supports ata-100, has softmenu III BIOS (1 mhz bus speed intervals), and plenty of room around the CPU for large HS/Fans. THe board also costs only about $100 shipped.