Bitbucket is a code hosting site, for the popular Mercurial version control system. With Mercurial, your data is distributed by definition, but you still need a place to share it, and keep track of your development.
Bitbucket is that. It provides a fully featured environment for managing development, including a wiki (naturally backed by Mercurial, you can clone it!), a powerful issue tracker, and easy collaboration with others.
Simply put, it takes the pain out of sharing code, and lets you focus on what you do best: Code.