Good Sam and other clubs

On my way home from picking up my TM2720SL I spent the night at an RV park just out of Nashville TN. Interesting experience as I did not even have a towel with me, but it was cool and cheap. The lady asked if I belonged to Good Sam as I was elgible for a discount if I did.
Does anyone belong to Good Sam or other clubs? Any advice as to benefits or other info would be appreciated.