Grace is a WYSIWYG 2D plotting tool for the X Window System and M*tif.

Jmol is a viewer for chemical structure data.

Lynx is a text based web browser.

Maestro is a graphic interface for Jaguar.

Ploticus is a free GPL software utility that can produce various types of plots and graphs.

PyMOL is an OpenGL based molecular visualization system

Smokeview (SMV) is a visualization program used to display the output of FDS and CFAST simulations.

surf is a tool to visualize algebraic curves and algebraic surfaces.