Asus A8N-VM CSM (Working)
Tested and working under ESXi 4 Update 1.
Motherboard: Asus A8N-VM CSM
Northbridge: Geforce 6150
Southbridge: nforce 430 southbridge
Slots: 1 - 16x PCI-Express, 1 - 1x PCI-Express, 2 - Regular PCI
Max Ram: 4GB
CPU: Athlon 64 3700+ (San Diego core)
Onboard network: Working
Onboard storage: onboard raid does not work correctly with ESXi, if left is SATA mode it works fine. If you need raid and have one of these boards on hand try different bios releases, it might work under a different release.
General motherboard review: http://www.pcstats.com/artvnl.cfm?articleID=1898