Git is a popular source revision control system. GitForce is a GUI front-end for the git command line tool and runs on both Windows and Linux. It is designed to be easy and intuitive to use and yet powerful enough so you don't need to use a command line git.
DocPosition is a content management system built for the web. It can be used to easily create and deploy large websites. It includes a set of components such as eCom, which is a complete ecommerce system.
hostingstar.com.au's open source software.
To be used primarily for dotnetnuke modules, a cross platform backup system, .net (dotnet) user controls, 3d plugins and many other bits and pieces.