ytDownloader
A userscript for downloading Youtube Videos.
This script doesn't require any external scripts or libraries, the code you see if the code you get.
It's very lightweight, pretty much working, just a bit ugly at the moment.
I will try to keep this version working as best I can, however I won't be doing any real modifications to it as my time will be spent working on the 'dev' branch.
Installation
Simply install one of the following: greasemonkey, tampermonkey, violentmonkey.
Click this link: ytDownloader.user.js
Your chosen addon should then provide you with an install option, once installed head over to Youtube and you'll find some links underneath videos.
Limitations
Due to the nature of Youtube, many of the videos you watch with a quality of 480p or higher, will actually be a seperate Audio and Video file, so while this script will grant you the ability to download all of these seperately, it can't merge them.
Video quality of 360p and lower are combined Audio and Video.