There's a tool for that. http://www.sears.com/shc/s/p_10153_12605_00952160000P
Bolt-Out from Sears
I have a set and they work well, they bite into the problematic piece of hardware and off it comes.
Try the sears store near you, they most likely have them in inventory.
TJ, Both methods will work & the Craftsmen set works excellent like Trikelady said.
Here are some other thoughts for you & others. Be sure to change the nut once you have it off. I know that may sound a bit obvious however I have seen & done it myself in a bind where the same nut goes back on only to rear it's ugly head later. Secondly try to always use a six point socket when possible. Less tendency to round off anything as compared to a 12 point.