Swiss army knife of image processing
Img is a collection of format handlers for the Tk photo image type.
Earth orbits and satellite coverage display in 3D on your laptop.
Doing 3D with Tcl
Open Source Solid Modeling CAD
PyMOL is an OpenGL based molecular visualization system
Panda3d to Tcl bindings
A C extension to Tk that provides functionality to modify images
Bulk Downloader for selectable Images (even Google Images)
Image viewer for animated GIFs
A Tcl/Tk widget for OpenGL rendering.