A bridge made of cardboard tubes. (First noticed on here.) It's more of an artpiece than utiltarian structure. Think rain and snow.
However the architect, Shigeru Ban, has built many utilitarian structures using low tech cardboard tubes. Protected inside an outer membrane, the tubes keep their strength and preform magnificently. For example,
This is a paper theater built in Amsterdam, Holland in 2003.
This one is a Japanese pavilion built for an Expo in Hannover in 2000.
Recycled hi-tech lace curtains. "Seen a few days ago in Cork, Ireland: a sensible use for all that bubble-wrap." Submitted by Tom Raworth.