Mercurial is a modern DVCS (Distributed Version Control System).
I recently started using it; it looks good, and easy to use, so far.
Mercurial on Wikipedia.
It is mainly written in Python, according to the Wikipedia article.
If you use it locally on your computer, you can also update your projects to Bitbucket, an online DVCS hosting site.
Bitbucket is by Atlassian, the company that is also behind JIRA, Confluence, and other software products for developers.
Bitbucket lets you create a free unlimited account which can support upto 5 users.
Bitbucket supports multiple programming languages, not just Python.
Mercurial book on red-bean.com
- Vasudev Ram - Dancing Bison Enterprises