Aerogel

POE is using it in their sleeping mats. However, word has it that the material is prone to flaking if handled roughly, so it needs to be protected (which POE does by encapsulating it). Because of this, I suspect it's use is outside the realm of DIY.

However, it's merits have been touted a lot, and yes a quilt could be wonderful. The one drawback is that it's not too compressible (if it's compressible at all). So, you're talking about taking on a pretty hefty volume penalty for said quilt.

Good point Joshua. I think a quilt might roll or fold up like a thin mat, but it would be very, very light.

There was a debate I think about "8000 meter" worthy boots in the mountaineering section that brought up the debate of Aerogel. Definatly a great idea for pads and insoles, I bet you could make a 3/4 pad that weight about 10 OZ for winter use if you figured how to work it