Fragmentarium is a really nice tool for goofing around with fragment shaders.
Awesome, I had completely missed it. A lot of people from FractalForums.com are thanked on the fragmentarium site. Really cool forum, used to spend a lot of time there when I dabbled in 3d fractals.
I keep meaning to toss together some examples that are game related rather than fractal or HQ images of some kind…need to motivate myself.
I like using GLSL sandbox. It has a really cool aesthetic, and is what got me into GLSL shaders. It has really taught me a lot about fractals!
Both heroku and shader toy are reasonable for the basics. The nice thing about Fragmentarium is: you can define basic UI elements for uniforms, you’re not WebGL, you can define a vertex shader and can use more advanced features like float buffers. It be really nice if there was a good modern replacement for RenderMonkey and <whatever nvidia’s tools was called) but I’m not aware of it if one exists.