Get a ThermARest, from Cascade Designs (widely available from REI, CampMor, etc.) They're the gold standard for sleeping pads. Here's a link to their web page.

I've got a 3/4 length Standard, & a CampRest. My preference is for the CampRest, in whatever incarnation it currently is--mine is more than 10 yrs old & still going strong. The newer ones have a more non-slip surface, but I keep my sleeping bag in place by using the rubberized mesh designed to be placed between floors & area rugs to keep the rugs in place between the bag & pad.

I've never had a bad night's sleep on either of my ThermaRest pads, but the CampRest is definitely better. I carry it with me whenever I travel, in case a hotel matress is made of plywood. <img src="images/graemlins/smile.gif" alt="" />

David