SiS648 - Not bad but has problems with 8x AGP working properly, ram running at higher speeds. The only decent board that works fairly well is the one made from Gigabyte. Also this board does not support Hyperthreading. (Which means that your 3Ghz+ chips will be slightly crippled) Plus, poor overclocking (Even with the Gigabyte)
Intel 845PE - No 8x AGP support but otherwise a fairly good chipset. If you go this route go with Abit IT7 Max Rev2. You'll get just about every feature you can think of or want on a motherboard. Sound, Lan, Firewire, A shitload of USB ports, serial ATA, etc. Another downside is it only supports DDR333, but it's still plenty fast. Also it's probably the best overclocker for Intel right now. There are other boards you can go with but I'd pick up the Abit with my money.
Nforce2 - Probably the best chipset out. If I were to pick a specific board I'd go with the Epox 8RDA+. But that's because I like to overclock. I'm sure you've seen plenty of info about this chipset. I'd say the only downside is the upgrade path.
Also you may want to wait about 2 weeks and see what the SIS655 chipsets look. Dont look at the reviews only wait until they get into peoples hands and see if other problems crop up.
Beauty is in the eye of the beer holder.