Filter Permissions
This module adds filters to the Permissions page to help manage a large number of roles and permissions. It can prevent submission errors related to PHP's max input setting and greatly simplify bulk permission changes when combined with browser tools.
This module provides filters at the top of the Permissions page for easier management when your site has a large amount of roles and/or permissions.
This has the potential to help if your permissions grid is too large to be saved due to the PHP max input setting as described: http://2bits.com/drupal/drupal-not-saving-admin-pages-large-number-input... and this module will disable submission if it would fail for this reason.
This can also be handy when combined with browser plugins that allow multiple checkboxes to be selected and checked at once. By combining module and role filtering and then being able to simply highlight the entire page of checkboxes, right click, and then "check" or "uncheck" you can greatly simplify the process of doing bulk permission changes.
If you aren't having performance issues due to massive permissions/roles and want a nice filtering solution that works entirely client side, Fast Permissions Administration is a slick module that has a different approach than Filter Permissions but will give similar benefits.