The Book of Shaders is described as 'provides a gentle, step-by-step guide through the abstract and complex universe of Fragment Shaders. Besides scores of insightful illustrations, the site includes a very intuitive live-coding editor for users to easily see changes as they code' and is an website in the Development category. There are more than 10 alternatives to The Book of Shaders, not only websites but also apps for a variety of platforms, including Windows, Linux, Self-Hosted solutions and iPhone. The best alternative is Shadertoy, which is free. Other great sites and apps similar to The Book of Shaders are Shader Editor (Free, Open Source), SHADERed (Free, Open Source), Shade - Pro Shader Editor (Freemium) and GSN Composer (Free).
Rayground is a framework for rapid prototyping of algorithms based on the ray tracing paradigm. Its main goal is to help develop, test and share self contained modules that showcase a particular method or technique.
ShaderTool provides a flexible and editable node-powered pipeline that allows you to write shaders without also having to have written an engine. Use the integrated code editor to directly write shader code in either HLSL (DirectX) or GLSL (OpenGL).
KodeLife is a fast, lightweight, live-coding IDE for shader development. It's available natively across Mac, Windows and Linux desktops and supports all flavors of OpenGL GLSL, as well as platform specific shading languages such as the Metal Shading Language and DirectX HLSL.