Read the Getting Started page to get up and running. You can use some language features right now and even try it out in your browser here. Just type in some code and see what Traceur produces. For an idea of what is available and what we have in the pipeline, see the Language Features page.
The JSConf 2011 presentation of Traceur describes the goals of the project and what it can do today. Some documentation is on the wiki on this site. Extra demos are in the source repository.
We also presented Traceur at NodeConf 2011. The video is available on YouTube.
Questions, suggestions, and comments can be directed to the discussion group.