Some tips: Start by considering what chipset you want. Intel havent made any that (officially) support PC2700. Via does not have a license (so very few bords uses this chipset). So that practically only leaves SIS. So checkout the SIS mobos from various manufactors and compare price/features. The chipset to look for is Sis645DX/961 (The DX version has support for 533 MHz FSB).
Unfortunately the 961 only provides USB 1.0. Sis has made a new chipset 948/962, that will provide USB 2.0, firewire, AGP 8x, PC3000 support and much more. But currently no mobo uses this.
PS: Dont buy, before you have considered Soyo Dragon mobos. They make same awsome feature rich boards. Im seriously considering the P4S645DX (SIS645DX) (533 MHz FSB / PC2700). Soyo has a Dragon with the 648/962 chipset scheduled for september.