Kent sent this in through the comments:

Plastiki is a boat built entirely from reclaimed plastic bottles will sail from San Francisco to Sydney. The project is intended to raise awareness of the human impact on oceans and other ecosystems.

The boat is made up of about 16,000 plastic bottles and is an “effort to raise awareness of the recycling of plastic bottles, which he says are a symbol of global waste.” says Rothschild. Skin-like panels made from recycled PET, a woven plastic fabric, will cover the hulls and a watertight cabin, which sleeps four. Only about 10 percent of the Plastiki will be made from new materials.

This won’t be quite as rustic as Kon-Tiki, but it looks like a fun time. They are planning a launch in the Summer of 2009.