Is This the End of the Alloy Bicycle?

No, no it's not. But these alternative material bikes sure are cool! We'll start with the plastics:

ha.

   But seriously folks, here are some pretty sweet plastic and composite material rides. This design is by industrial designer Matt Clark. According to the article, his vision is to mass produce this bike as cheaply as possible using recycled materials. How very Southern California, where the design originates.

The IV-1

   Next is a bike produced by Saab called the DINGS. Theres not a ton of information on this bike out there, except that it was a prototype and was built in 1981.

Saab DINGS

   I really like this view of the bike showing the structure of the frame. 

Underside view

And now for the wooden entries! Plenty of wood bikes have made the rounds, so we're going to focus on three of the coolest. First, there has to be more of these wood bikes than any other type:
wooden one:

Getting them hooked young

   Next - this has to be one of the coolest designs I've seen.  This is the Splinter Bike:

Splinter 1

   IN this CAD drawing you can really see how the drive system works. The crank turns a massive, 128 tooth ring that drives the rear wheel:

CAD Drawings

   Lastly, a nice little angle shot:

Wood stand, naturally

   Lastly, here's a gravity bike from Polynesia. This pic has been floating around the web for a while now, but no less cool for it:

Foot brake!

   All of these are sure forward thinking. Someday maybe we'll all be riding plastic bikes!