Pyrite (fool's gold) is an attempt to get the best of both git and mercurial. Git excels at speed and flexibility with repo history. Mercurial excels at ease-of-use and support of non-unix platforms.
Like Mercurial it will be written (mostly) in Python, offer extendability to people who want to add functionality and have a built-in webserver for sharing and viewing your projects.
However, it will be built using the git data structures so that it can offer more flexibility in managing your history. It should also be compatable with git so that people can move from one to the other with little difficulty.
License GPLv2
The main pyrite repo
pyrite user forum and development list