Some of the available filters are listed in the [WordPress Codex][1]

[Adam Brown][2] hosts a much more complete list of action and filter hooks.

You can also search through the source, as @toscho [mentioned][3].

   [1]: http://codex.wordpress.org/Plugin_API/Filter_Reference
   [2]: http://adambrown.info/p/wp_hooks
   [3]: https://wordpress.stackexchange.com/a/76247/19726