Firefox with Greasemonkey only: The YouTube H.264 user script adds a link to view and download the higher-quality version of YouTube videos in page. You already know how to hack YouTube URLs to access a higher resolution and audio quality version of a clip, and this script makes downloading the HQ version easy. (See the difference between regular and HQ videos.) Be warned: This script can take time to render the links (sometimes it hangs indefinitely), and the HQ version isn't available for all videos. Once the kinks get ironed out, I'll add it to the Better YouTube extension. The YouTube H.264 user script is a free download that works with Firefox and the Greasemonkey extension.