This is a tiny slice of some of the best, most notable, and occasionally most GPU-crushing shaders available on the GLSL Sandbox Gallery. Not all of these shaders work on all hardware, and a beefy graphics card is required for any of them.
This list is still growing, and likely doesn't include your favorite shaders yet. If you'd like to see them added here, drop me a line on Twitter as @emackey or send me a pull request on the gh-pages branch on GitHub.