Instead of editing .htaccess, adding this to functions.php
in a theme allows you to add rewrite rules. Remember to update
permalinks settings to activate any changes to these rules.

Syntax: add_rewrite_rule($rule, $rewrite, $position);

Details: http://codex.wordpress.org/Rewrite_API/add_rewrite_rule

NOTE: If you add custom query variables, you'll need to
register them using add_rewrite_tag()

// Used with a custom post type