The Cannondale onBike straight up pushes the bike design envelope. Cannondale replaced the seat and chain stays with an enclosed single sided chain case. Pretty awesome. The chain case is made of machined billet, so they bascially took a hunk of metal and machined it into a chain case. The bike is a 9 speed with internal gears and disk brakes.
They call it "Case Closed Technology" (pretty cliche, but gets the point across) and it allows for a maintenance free drive system. Kind of scary because maintence free would make TheBikeTube obsolete! Of course this bike does cost something around $6,000 so I'm not too worried.
The original design was made out of carbon and was foldable, but Cannondale thought it might be too expensive for a production bike so we now have the design pictured above and a much more reasonable $6,000 price tag. Woo, gonna get me one tomorrow....