Are you looking for high OC'ing or a more economical board? High OC 790FX boards (and soon, the 890FX boards) are fairly expensive running $165-180. The 790X boards are the next step down and are very popular for reasonable prices ($105-140) as well as good OC's. I would pass on the 790GX boards unless you want on-board video or are looking for a cheap, but fair, OC'er. In any case I would also look for good MOSFET cooling. Many boards, especially the cheaper ones, have no heatsink on their power chips, which is never a good thing if you'll be cranking up the vCore for a better-than-average overclock. I'm sorry to say none of the nVidia boards have a good record for more than average OC's and AMD chipsets don't allow SLI. though you can run any single video card on them.
Gigabyte has really stepped up to the plate with the AMD 790X and 790FX chipsets. ASUS also makes some very good boards (as well as a few OC duds in the G/GX series) and MSI has one or two that are also good clockers. DFI boards have been a let-down, to say the least, with bad BIOS updates and some other odd issues - I'd skip them this round. Biostar makes a couple of good boards in the lower price range.
As col_sanders just hinted, the 890X and 890FX boards will be out in about a month. No word as to how much better they are, if any, over the 790X and 790FX for overclocking ...