Grafeo (formely OpenGrafik) is a free software diagramming tool (free speech and free beer) aiming at making diagram creation, editing and viewing as easy and pleasurable as possible. You may regard it as an alternative to applications like Kivio, Dia, SmartDraw or MS Visio. Grafeo is written in C++ using Qt.
We use a git repository on Gitorious that can be cloned using: git clone git://gitorious.org/grafeo/grafeo.git