We use VSS in house, but as it is not reachable outside (as in from home) and since I have no great feelings of love or excitement for CVS we actually do it the old fashioned way. We have the files in a common repostitory. When I work on them a I make a copy, do my work, document every line I change and then Charles and I sit down, review my work and add it into the main source files.
It truly is a pain in the rear and we are really looking for a better way. So far we haven't found anything we really like.
