+1 for the Therm-a-Rest Z-lite Seat Pad that @REI-JohnJ mentioned. After arguing (with myself) back and forth about dropping the $40 on mine, I now take it everywhere with me. I've sat on wet tree trunks, barely dried up mudholes, frozen rocks and just about everything else. It doesn't actively heat the bottom but it does keep it from getting frozen or wet (be careful in the mudholes : ) ).
one or more gifts or other benefits from the co-op.