NC is a very long state, but in the Northwestern end I like to ride on Stone Mtn, which is along the NC/TN state line. Lots of good logging trails.
Also, there's a new OHV area opening just across the state line in TN. It's called Doe Mtn. It runs between Mtn City & Watauga Lake, and is 8600 acres & about 15 miles long. They aren't officially open yet, but plan to have around 150 miles of trails. They should "officially" open in 2013 or 2014, but folks are riding there some now. It's beautiful country there & Watauga Lake is a real gem if you have a boat. Doe Mtn is only 30 minutes west of Boone, NC.