The "Arantix" mountain bike from Delta 7 Sports uses an open lattice tube design made from carbon fiber and kevlar. They call the technique "IsoTruss."
From the press release:
Each Arantix Mountain Bike frame takes approximately 300 hours to build, as Delta 7 Sports workers weave single carbon fiber strands to create the open lattice IsoTruss structure of each frame tube. Each bundle of carbon fiber strands are wrapped with Kevlar and then baked at 255 degrees Fahrenheit for four hours. The ends of the baked tubes are then machined before being joined with molded carbon fiber lugs to make a complete frame.
The completed frame weighs just 2.75 pounds.
Delta 7 Sports plans on shipping just 200 Arantix bikes in 2008 with a price of $12,000 fully kitted out or $7,000 for the frame alone.