K-3D is the free (as in freedom) 3d modeling, animation, and rendering system.
Sodipodi is general vector illustrating application for Linux/Unix and Windows. It uses W3C SVG as native file and in-memory image format and can do many neat things.
A UML class diagram editor written in C++ using Tcl/Tk for the GUI portion. Designed to be easy to maintain and extend.
Convey is a real-time, online, multi-user collaboration tool which augments text, graphics, and symbols. Examples of graphics include shapes, mathematical expressions, diagrams, flow charts, and pictures.
The Doodle project aims to provide a language to easily describe Origami diagrams and produces a ready-to-print document. Doodle will free creators from diagramming constraints and increase their capability to share their creations.
AudioCarver is a music composition application featuring a user interface based on 3d modeling.
Debrief is an Open Source Java application used for viewing maritime vessel tracks in 2 and 3 dimensions. Tracks are read in using a number of flat-file ASCII formats, including AUTEC (RAO), PMRF and AFWTF.
Varkon.Org is a resource site for users of the Varkon parametric CAD and modeling system. This site is a mirror and archive for the Varkon.Org site. You can find all versions of modules for use with Varkon on this mirror site. See the website for info.