Tools for Collaborative Development
The collaborative development of open source software, so far, are made with an online repository where they are stored under a system version control, IRC for communication between developers and a bug tracking system. Thus, anyone who wants to help developing the software get in touch with other developers on IRC, download the code from the repository and see the pending list on the bug tracking system. So now the code part comes. This proves that this method works very well.
But when it comes to games, this method might not be enough. Especially because the team is usually fixed, and there are game designers, artists, musicians and other people doing different roles in the process.
These tools are really useful to a game development team:
Communication between team members can be all done by Skype . Especially by voice. It is useful throughout all the development process.
Skype also has some other utilities, for example, the Windows version has a remote screen viewer. Unfortunately he is not well developed for other platforms, but the issue of remote screens is simple, we shall see it below.
The Google Docs allows you to edit documents collaboratively and there are several options: you can invite only those users who want access, or let him free so that everyone can edit. You can also leave the document as only reading.
You can create diagrams in general in Google Docs, but is somewhat limited. Cacoo, in the other hand, has many options for creating any type of diagram. It is very useful in the planning phase of the project.
Version control system
There's nothing like having a public storage place among all team members. The code is being versioned, but what about other resources related to the game?
The Dropbox is an essential tool in any context, talking about development it becomes even more evident.
Remote screen viewers are very important. If you're doing pair programming, or even as a troubleshoting procedure. TeamViewer is one of the bests solutions.
If you want to read more about the OpenSource development process, you can freely download the Producing Open Source Software book.