Just got the below spec working with ESXi 4.1 u1 (348481), thought I'd share...
Motherboard: Zotac H67-ITX-C-E Mini-ITX (socket 1155, WiFi, 6x SATA)
Processor: Intel i5-2400S (65W TDP 2nd Gen i5)
RAM: 8GB (2x 4GB DDR3 DIMMS)
Boot Disk: 1GB SD-Card (USB2)
Datastore Disks: 2x 2TB Seagate Barracuda Green SATA-600 64MB 5900RPM
Case: Chenbro ES34069 Mini-ITX case (4x removable drive bays, for a bit of future expansion if needed)
Was surprisingly straightforward. Only addition required was oem.tgz for the onboard Realtek NIC (8111/8168). I used the one on this (vm-help) site. Thanks for the effort with documenting and compiling drivers, makes installing ESX on whiteboxes, MUCH easier http://www.vm-help.com/forum/viewtopic.php?f=12&t=1272
Went for the Zotac mobo a bit on a whim and without much investigation, as wanted a Mini-ITX board, low power (but with plenty of horsepower) CPU, and more than the usual 4x SATA ports. This one can take any of the new 2nd Gen 1155 processors, can take 16GB RAM (tho 8gig sticks are bit expensive atm) and comes with 7 (2x SATA3, 4x SATA4, +1 externally mounted eSATA).
Have the 2x hard disks attached to the 2x SATA3 ports and works fine, although haven't had a go at seeing of the RAID functionality will work in ESX or not, that's the next step )only want mirroring).
The case is a welcome surprise, well built and nicely laid out.
PS. This box will replace a ESX3.5i running on an old Dell Optiplex SX270 (2GB RAM, P4 HT, etc), that I have had running for years, but that was super simple to install even back then, as it has *ordinary* Intel components that ESX is OK with.