There's a section here named "Members Deals"
Most forums have a selling area. I wish there were occasional "Off Road" themed swap meets to go walk around.
If you drive north a bit to Pomona, there is a car swap meet at the Pomona fairgrounds once a month. Their geared towards classic cars though. I haven't been there in years. I keep wanting to go see if anything interests me. With Off Road being a bit of a fad again, there may be stuff to see now. In the fall the Pomona Off Road show will be coming around again. Nice place to find new gear. They do tend to be more desert race unfortunately.
Scott