FIC offers Micro BTX board for Socket 939
FIC has produced a Micro BTX motherboard for Socket 939 Athlon 64 processors. The KTBC51G supports dual-core processors, has PCI Express x1 and x16 slots, and appears to use NVIDIA's GeForce 6100/nForce 410 chipset. Gateway is already using the board in one of its systems, although the model in question appears to only be available in Japan.
BTX has yet to really catch on, but the design does some fundamentally good things with air flow and component placement. It will be interesting to see what happens to the form factor as Intel shifts its focus to performance per watt.