If building AMD, get a socket AM3+ board with a 900-series chipset. It will support a Bulldozer upgrade if desired, has all the latest ports and connectors, and will support SLI as well as Crossfire.
I am using an Asus Sabertooth in my AMD machine: http://www.newegg.com/Product/Product.aspx?Item=N82E16813131736
. I like the 5 year warranty, and I can't imagine finding any device any time soon that I wouldn't be able to connect to it. With a Xigmatek Gaia cooler, my X4 970BE oc'ed to 3.8GHz is currently idling at 31C.
The cheapest one I'd consider is this ASRock fpr $105, because it supports Crossfire/SLI at x8,x8 rather than x16,x4: http://www.newegg.com/Product/Product.aspx?Item=N82E16813157262
Edit: added CPU.