I would like to recommend an AMD 785 board. Specifically the GIGABYTE GA-MA785GM-US2H, as its only $70 ($85 when not on sale) USD which isn't exactly that much for a relatively good motherboard.
The board doesn't work out of the box with coreboot with similar boards selected nor officially supported by coreboot at all, however you can use 99% of the code for the MA785GMT-UD3H by GIGABYTE and edit devicetree.cb and Kconfig a bit and it works just fine, but only with 1GB of DDR2 memory (just like the ASUS M4A785-M.) SeaBIOS crashes otherwise.
If you want to do coreboot work, you can try writing a fix for that, that way you would actually hit 2 birds with 1 stone ;)
This does mean that an AMD Fam10 series CPU would have to be at hand though and I know the original poster mentioned an Intel chipset...
-Alec
--- On Thu, 1/13/11, Peter Stuge peter@stuge.se wrote:
The chipset is not supported at all and requires new support to be written.
I would, again, recommend looking at hardware which is already supported.