If you stay on the ground try using a POE Ether, a Big Agnes Insulated Air Mat, a Stephenson Down Air Mat, or Down Air Mat 7. I believe that all of these come in right around or under 2lbs and give you 3" of insulated air mattress under you. (When on the ground I use the POE Ether long which comes in at 22 ounces). Someone else who carries one can chime in on chairs.

The other possibility is to move to hanging (using a hammock). They are very comfortable to sleep in and can be used as a chair to relax in. The warbonnet Blackbird seems to be the premier hammock right now http://warbonnetoutdoors.net/ but other asym hammocks, bridge hammocks, and end gathered hammocks are all possibilities. Check out http:/www.hammockforums.net for ideas. I find them the most comfortable way to sleep.