The best method to download YouTube videos

I like to download lectures and presentations from YouTube so that I can play them back using VLC at 2x playback speed.

My favorite option for downloading is this YouTube video download GreaseMonkey script that adds a download button to the YouTube video page. It works in Chrome, and in Firefox with GreaseMonkey. This is vastly superior to the more-popular YouTube video save sites that require to you execute a sketchy Java applet.