Need BAT form factor? Only one choice - DFI K6BV3+/66-2.
In ATX, there is a wider choice of decent boards with 2 MB L2 cache and UDMA66: Epox MVP3G5 (1/5/2 AGP/PCI/ISA slot configuration), DFI K6XV3+/66-2 (1/4/3) and Tyan 1598-2 (1/5/2, 4 USB, and optionally onboard sound).
All those boards use the VIA MVP3 north bridge and the VIA 596B south bridge, with the exception of the Tyan which uses the 686A south bridge. There is a marginal chance that the Tyan will be updated to use the 686B for UDMA100 IDE support, but don't hold your breath.
Regards, Peter