Shaders/Before 1.9

Shaders are a feature being added into the 1.7 update, and currently exists in the 13w38a snapshot. Later snapshots from 13w38x support shaders, however, it seems that only the "a" build has the files included with the download.(requires testing.) You can switch between them by pressing the "Super Secret Settings..." button under options in the menu. Although it doesn't work for some people.

Shader