View all WP query variables
Micro Tip for the day: slice of PHP code for viewing all WordPress query variables. Very useful for figuring out custom loops and such.
Just add this in any theme template file, for example just before the WordPress Loop:
global $wp_query;
var_dump($wp_query->query_vars);
Check out View all WP Post variables to learn more.
More tuts + trix on the way :)