Shader Maker is a simple, cross-platform GLSL editor. It works on Windows, Linux, and Mac OS X.

Lumina is a free crossplatform development environment for GLSL shaders. An ECMA script based language is used for tools and rendering control. Lumina provides maximum flexibility that allows the user to build renderer prototypes for deferred shading, depth peeling or HDR rendering, as well as vertex shader and instancing accelerated bezier objects, skinng or GPU based particle systems.

Visual node-based editor for DAGs.

Sler is a RenderMan shader generator and a shader testing suite.