I would also suggest a hammock to use as a seat if you're hiking in a wooded area. The Byer weighs in at 11 ounces, and for the weight and cost you won't find anything as comfortable. Setting up is a breeze once you do it a couple times.

http://www.byerofmaine.com/amazonas-traveller.htm

Of course if you really don't like hammocks, there are other options. If you hike in a area with active bears, a bear cannister also doubles as a fantastic seat. Not as light, but serves double-duty in keeping your food safe.

And for folding stools, Byer also makes a very packable stool that weight in at 21 ounces...

http://www.byerofmaine.com/s-trilite-xl.htm

Hope this helps!