Salt includes a number of built-in external pillars, listed at Full list of builtin pillar modules.
You may also wish to look at the standard pillar documentation, at Pillar Configuration
The source for the built-in Salt pillars can be found here: https://github.com/saltstack/salt/blob/develop/salt/pillar
Current Salt release: 2014.1.6
Docs for previous releases on salt.rtfd.org.
Full list of builtin pillar modules