Pig Trails? I'm assuming that's a regional thing.
VVMapping is a company out of Michigan that creates gpx files that are programmed to lay over the top of Garmin's build in road files. You upload their map to your GPS. Fantastic product that is reasonably priced, works fantastic, and is made by a company that RIDES. These guys started this company because they wanted something for themselves to use.
Great Lakes ORV Trails (MI, MN, WI, IN)
GPS Maps
Appalachia ORV Trails (WV, KY, VA, TN, OH, NC, SC)
GPS Maps
http://www.vvmapping.com/