What little glassing I do, I use a Crazy Creek fabric chair. Use it mostly when calling critters.
^ This has worked fantastic for me, though mine is a Cabela's branded knock-off "canoe chair". Same thing though.
It's essentially what Calvin suggested but allows you to recline a bit. They're virtually weightless, strap across the back of my pack, fold down flat so they take up almost no space, and set up in seconds.
Only drawback is they don't get your butt off the ground so in cold weather they're tough. Also they give you no elevation so in thicker vegetation you need to find a stump upon which to set them.
