Terrain Software and Projects - Noncommercial
see also: commercial software and government/academic projects

WebGL

In March 2011, the WebGL platform became available for doing OpenGL directly from JavaScript in a supporting browser (Firefox 4 or Chrome 10) - 3D with no plugins.  Very quickly, some geoviz applications appeared for it.  Because the software runs on the client in JavaScript, they are effectively open, and to date all non-commercial.

Older / Historical