Twitvn is a small Python script that, when used as a Subversion post-commit hook, will publish commit messages to a Twitter account: http://code.google.com/p/twitvn/
Why would anyone want to do this?
There are many reasons. It would help foster collaboration on a multi-member project, either allowing them to follow the Twitter account with their own, or via Twitter's RSS feed. It could also allow interested users of the project to follow status updates of what is going on with the project.
Finally, it's just a damn fun idea.