Is there any version control system / subversion system that allows you / the group to check the latest version and then work together on it simultaneously? I think something similar to how Gobby works in terms of allowing everyone to edit the document at the same time, but more of a "repository" if that makes sense.
svn and bzr, and possibly cvs, all this resolves, however resolving conflicts can always be tedious if you all work on the same piece of code.
Do you mean something like Etherpad ?