Besides the MSI SiS 645 chipset board (nice looker, BTW), look for VIA P4X266/P4X266A chipset boards. Yes, the A version is faster, but you can find some real deals for the older version - and it's still very fast. I got an Azza board using the older version (yes, it got bad reviews, but I didn't have any problem with it, YMMV) and my system with this board, P4-1600 (OC to almost 1700), 512MB Crucial DDR and an original Geforce 256 SDR video card got almost the same Q3 framerate as my buddy's AthlonXP 1600+ (OC a bit also), 512MB Crucial DDR and an ATI Radeon 7500 (faster retail box version). We're talking about 5% difference. My Azza board has been pretty stable. Strangely, it UNDERvolts the CPU to around 1.71 vcore, and there is no manual adjustments. The FSB can go in 1MHz increments to 132MHz.
For all of you recommending AthlonXP setups, I agree that the AthlonXP give much more bang/buck, but I went with the P4 (only in one of my many systems, hehe) for a reason. I've found, whether due to CPU or motherboard I don't know, that P4 systems overall seem very stable. Sure, I've seen many Athlon systems as stable, but I've also seen some not too stable. Also, the P4 setup runs COOL and SILENT!!! The retail-boxed Intel fan/heatsink runs so silent that from within a case you cannot hear it. Even running it outside a case (with a power supply that has a dead fan - we use for temporary testing only) you cannot hear it until you are about a foot away from it. It's REALLY THAT QUIET, and the heatsink stays COLD to the touch when the system is idling, and barely warm after some intensive stuff. Yes, not everyone cares. I don't care that much either, but I needed a quiet system for only ONE of my computers, and the P4 fit the bill.