Therm-A-Rest hiking mattress. Most sporting goods stores have them plus Cabela's on-line. They are self inflating and very light for backpacking. We like the shorter ones (top of head to knees)to keep size and weight to minimum. Don't over inflate and keep covered with towel - the sun will heat and overinflate. Mine is approx. 10 yrs old used approx. 4wks a year on the beach and still doing well.
Yep, 15 yrs of 4 wks/year for ours. Also use a nylon strap to hold them down. We keep it down there in our CO storage box (for which they now charge an annual fee) <img src="http://www.traveltalkonline.com/forums/images/graemlins/thumbsdown.gif" alt="" />
