Thermarest sells a little patch kit that works like a champ. You prep the damaged area with an alcohol pad, then boil a pot of water, then apply the glue to the patch, stick the patch over the hole, then set the pot of hot water on it. When the water cools, you are good to go. The problem sometimes is finding a pinhole leak if you don't have water to dunk it in.
That's great, but I took my "leaking" Thermarest pad back to Sportsmen's Warehouse in Phoenix and they offered me an upgrade to a better pad and I actually was able to get some money back, too.
