I found this guy pretty comfy after picking up at an REI garage sale:
Thought I wouldn't like it vs one that is air+foam, but it worked well.
Not marketed as being a backpacking or ultralight pad, but it packs down pretty small and really doesn't weigh much. The built in pump works well enough (although if you want to attack it with strong lungs, you will be done faster).
But if you have already...