Salt includes a number of built-in subsystems to generate top file data, they are listed listed at Full list of builtin master tops modules.
The source for the built-in Salt master tops can be found here: https://github.com/saltstack/salt/blob/develop/salt/tops
Current Salt release: 2014.1.6
Docs for previous releases on salt.rtfd.org.
Full list of builtin master tops modules