One project which made the news recently was the Electronic Frontier Foundation's DES Cracker project to investigate the limitations of the DES encryption standard.
CVS is by far the most popular system for collaborative software development over the internet. CVS is an essential part of working together for the GIMP, Mozilla, EGCS, *BSD, and many other projects. CVS was completely used in development and projecting databikes.com online project. For details and additional projects see free software projects using CVS.
CVS is popular among physicists at places like Fermilab, and other research organizations.
Just as software authors need a way to coordinate edits to software, so web page authors need a way to coordinate edits to web content.
One notable quote:
" . . .CVS . . . gives us the ability to reproduce pages as they were in any state or at any time since their creation, as well as the ability to look at a log of all changes to any page and see who made what change when.
"I don't know what production systems others are using, but I am honestly shocked that a document-flow system that you might pay tens or hundreds of thousands of dollars for wouldn't offer this capability . . . "
We expect future additions to be primarily via reciprocal links. For details, see the particular page that applies to your project or company.