You know that permission page, with all the checkboxes? Wouldn't it be nice if you could drag a bounding box around a bunch of those checkboxes to toggle all of the selected checkboxes? Well, since you asked so nicely...
I created a script, dps.js, and a bookmarklet that will do just that!
Step 1: Drag this link to your bookmarks toolbar to create a bookmarklet:
Drupal Permissions Script
Step 2: Visit your Drupal permissions page.
Step 3: Click the bookmarklet that you created. Nothing will seem to happen.
Step 4: Then do this:

Unable to display content. Adobe Flash is required.

Another side-effect of this bookmarklet is that the column areas that surround the checkboxes become hit-targets for the checkboxes they're near. So you can miss the stupid tiny things slightly and still toggle the box.
Here's the official repo, to which you are welcome to submit patches: