Christian Neukirchen describes a useful procedure for how to set up tracking of foreign CVS repository using Git, cvsup and cvsps 2.1. He uses the Ruby CVS repository as an example. The resulting GIT repository takes 29 megabytes and contains entire Ruby development history for eight years.
Read more at Tracking the Ruby CVS with Git.
P.S.: I had to install newer cvsps, and to edit the CVSROOT/config file, removing LockDir config option. Give git-cvsimport a -v flag to see what it is doing.