Bamboo is a lightweight, fast growing material for pioneering, that is available relatively cheaply in most tropical regions of the world. Flickr.com has some incredible photos of projects built with bamboo.
First, Duncan Hodges' photo of a bamboo tower in Oxford:
Hoffa534 has a great photo of the bamboo scaffolding that is common in China and much of the Far East:
Michaelbrandon has a photo of a bamboo raft in Thailand:
...and Kandyjaxx has these details of the lashings holding a bamboo raft together
Finally, Ed Fladung has this photo of a bamboo bridge in Vietnam:
There are (literally) thousands of other photographs of bamboo structures on Flickr, and the Bamboo (bambu) photo pool is a good place to start if you want to see some of them. There's also a great book called Build Your Own House which is available on Amazon.com, that has great photographs and drawings of buildings constructed from bamboo.