You need to consider what kind of repository system your team needs to function effectivly. The main difference is between:
- Centralised Repositories - CVS, SVN, Simple File Server, etc
- Decentralised Repositories - Git, Mercurial, Bzr
I make this distinction now, because if you move from cvs to git, you will need to read up on what it means to have decentralised repositories. The new kinds of work-flows you need to develop will make development easier and more efficient for bigger teams, but the change in workflows will make your first attempts fail as you make assumptions about how it's supposed to work.
Here in the Ubuntu world we use Bazaar (bzr) which is a very good decentralised system written in python and based on mercurial. It's fairly easy to set up a server and the commands and extensions available are well developed. Eclipse has a very good bzr plugin. Launchpad and GNU's Savana use bzr by default and it's my personal first choice.
Git is also another fantastic repository system. Developed by Torvalds himself after his disastrous time with a proprietary system, GIT is lightning fast and only slightly harder to use than bzr. It's used by github, gnome and several other projects as their main repository system after using svn.
Both are available in the Ubuntu repositories, as well as a ton of extensions.
I wouldn't use svn or any other centralised repository unless you have a very small team and know what you're doing.