ShaderFrog

Shader Frog lets you create visual effects by composing two or more shaders together, and tweaking their parameters. You can build a complex effect out of simple components. You can then export your shader for use in your THREE.js game or application.

Shader Frog gives you a repository of user generated shader content, so you have a variety of effects to choose from. With Shader Frog, simply search until you find another shader that you like. Selecting it composes the two shaders together. You can tweak the parameters of the input shaders to create the exact effect that you want. Now you can export this new shader to your 3d game or application.