SHADERed
Lightweight, full-featured desktop tool for creating and testing HLSL and GLSL shaders
3 Alternatives To SHADERed
KodeLife
Real-time GPU shader editor, live-code performance tool and graphics prototyping sketchpad.
ShaderLab
WebGL2 GLSL Editor for the browser.
Shaderific
Create shaders on the go with the OpenGL shader development app for iOS