Hgfs is a read-only filesystem interface to Mercurial repositories. The interface gives access to the commit message, manifest, and files of each revision, and to .tgz's of each revision (the .tgz's are generated as they are read). The filesystem is a front-end for the Mercurial library that comes with it. All code is written in Limbo, for Inferno.
RhodeCode (formerly hg-app) is a Pylons framework based Mercurial repository browser/management with a built-in push/pull server and full text search. It works on http/https, has built-in permission/authentication (+ldap) features. It's similar to github or bitbucket, but it's supposed to run as a standalone hosted application and it focuses more on restricted access to repositories. It's powered by a VCS library that can handle many various version control systems.
AgileSCM is an application lifecycle management solution for Subversion, Git, and Mercurial. It allows you to spend more time developing and less time fighting development tools or tied up with administration. AgileSCM is a user friendly, browser-based interface which abstracts developers from the complications of SVN, Mercurial, and Git.
Mercurial HeadQuarter is a Web service for managing Mercurial repositories. It allows the user to define contact names, define project descriptions, set up access (read and write), set which types of archives are allowed, define encoding charsets, hide/unhide projects, set the presentation style, and redirect access and error logs to files.