Manual, Wiki and more
The Snakelets documentation is currently very simple. But as it is written in Python, and contains comments in the source, you should be able to figure out a lot from the source. A short quick-reference guide to all relevant methods is included though.
The 
quick reference guide for Snakelets is also available online here, so you can have a glimpse at it without needing to download the package.
Detailed Snakelet project information can be found at the Sourceforge 
project page. (There is also a 
mailing list for Snakelets, and a separate mailing list for webapps).
There's also a 
Snakelets Wiki for more dynamic information about Snakelets. Because it's a Wiki, everybody can contribute to the contents of the pages. It's currently running on a server at home, so it's not extremely fast or reliable, but hey :-)
Are you interested in the performance? Have a peek at some Benchmarks that I've done.