There are many candidates here, actually. Cheapest one would be Asrock X79 extreme9 :
http://pcpartpicker.com/part/asrock-motherboard-x79extreme9
Then as the price climbs up, we have ASRock X79 Champion, Asus P9X79 WS, MSI Big Bang - XPower II,... till we meet the last boss, ASRock X79 Extreme11.
Here's the list of LGA2011 boards being sold atm : http://pcpartpicker.com/parts/motherboard/#qq=1&s=21&sort=a6