How light do you want to get? I have a Downtube 8H folding bike that weighs 26.5 lbs stock. You can knock off a few pounds by removing the rack and swapping out the front suspension fork. It comes with a Sturmey archer 8 speed IGH. It's around $400.

http://www.downtube.com/Font_Suspens...ding_Bike.html