Bitbucket is a popular code hosting website that up till now used to be Mercurial-only, but has now added support for Git as an alternative. Like GitHub it offers both free and paid plans for code hosting. For those who don’t know Mercurial is a Python-based distributed version control system that predates Git.
While GitHub, and most other such code-hosting websites offer unlimited free hosting for open source projects, and limited or no hosting for closed or private projects, BitBucket allows one to create unlimited private projects.
The website offers a per-project bug tracker, wiki and other features, and recently has added support for threaded commenting for changesets and pull requests. This allows developers to have discussions around code changes in the repository. BitBucket has also made numerous changes to the UI to make it easier to use.
Git is becoming increasingly popular, and it was only a short while back that Google Code too added support for Git.