Xeon X5670? I think the X8 series of SuperMicro should do: http://www.supermicro.nl/products/motherboard/Xeon1333/#1366
Specifically I'd go for this one: http://www.supermicro.nl/products/motherboard/QPI/5500/X8DAL-i.cfm
Other than that, here's Tyan's range of Xeon DP boards for 1366 socket...
OK, here's my 'Dually rig':
My 2nd workstation is a dual Xeon Prestonia (2.4 GHz, LV, 40 W TDP each) setup with Windows Server 2008 Enterprise an 8 GB ECC Reg DDR-266 RAM (4x 2 GB) on a SuperMicro X5DPA-GG Board, 2x WD Blue 160 GB HDDs, HP dvd630 toaster, Matrox Parhelia PCI-X graphics, SB Live...