after some research, we opted for working with Drupal on our next project and we are a distributed team.
Since Drupal stores (based on what we saw until now) all it
Simpletest is an invaluable tool as a developer who's working on module "A" can run the test suite and be sure he/she has not broken module "B" and then commit (for example). See the Simpletest module and Selenium IDE. Test driven development pays off in more ways than one. Developers gain confidence and can work faster/better.
Some good issue tracker and/or project management software can keep all the project info centralised and facilitate communication between developers. A wiki is good too. Emails between project managers and individual developers don't keep everyone in the loop and can get lost in time, in a noisy email environment.
I like developer chat rooms for distributed projects. Chatting in real time is very handy. Some version control can write commit messages to chat rooms.
The backup_migrate module is handy to grab the latest DB fixture off the production server. Of course you can export through mysqldump etc but this little module is a no brainer.
Check out doxygen too. Force your developers to write to that format. And pay attention to the drupal coding standards. There is a module called "coder" than can check it.