I just created my first project on sourceforge.net, namely QUnit. To create a new project you have to fill in a form with some info. After a couple of days your application might be accepted, and then you get ssh access and full control over your project site. Default setup is to use CVS, but using the admin interface it is easy to switch over to SVN and seconds later you can just check in your code. I am quite impressed by the system. It does really work, and the system makes me feel welcome.
Using sourceforge.net I wonder how it would be to work in a company where all software development was based on developing software by managing projects the sourceforge way instead of having a massive shared repository. There must be plenty of pros and cons, but I think it could work quite nicely.