Here's an awesome mud run/obstacle course race, called the Firebreather Challenge! You'll be climbing walls, dragging a sled, and slogging your way through the Durham Fairgrounds. Here's a link to sign up for the race:
There will also be an added fitness class for participants, which will get you prepared for the obstacles and running that you'll encounter along the way. Send me an email if you're interested in signing up for the new class.