CVSBrowser provides web-based access to view CVS repositories, based on the cvs 'modules' file to more accurately reflecting the repository, and handling multiple repositories with individual configurations.
It is written in PHP and uses rlog as the backend. In this way it is very much like other cvsweb-style projects. The difference here is the focus on correctly representing the cvs 'modules' file, which allows for modules to have different names/working directories than the directory names on the physical filesystem.
This functionality is particularly useful to administrators of large, complex projects. I speak from personal experience.