FlightGear Flight Simulator: free open-source multiplatform flight sim
A portable, multi-platform, command-line driven graphing utility
Open Source Solid Modeling CAD
Pencil2D is a cross-platform animation/drawing application.
Free yourself
A taggable image board written in Rails
3D .NET engine for Windows, Linux, Mac
A panographic toolkit compliant with open source standards
Web based image gallery for enterprise product showcase.
Hand Written Equation Creator
Game engine supporting many 3D/2D formats and graphic effects