Subversion is a new version control system that may very well replace CVS as the tool of choice. Version 1.0 looks promising, but I'll stick with CVS until they finish coding/debugging the features for the 2.0 release.
ViewCVS: Viewing CVS Repositories is an all around helpful tool for managing your CVS repository. Although certain CVS clients can do all of the functions of ViewCVS, it's nice to have it all on one screen and to be able to e-mail links to versions/change logs to other members of your development team.