Long time ago i shared about KissYouTube in which you just had to add kiss before the url to download it, now a similar simple service is available which you can use to download YouTube videos in the standard quality FLV or in high quality MP4 format without using any programs or FireFox extensions.

How to Download YouTube Videos easily:

Just add "pwn" before the youtube url and you are ready to go, see image below

You will be presented with the options for downloading YouTube videos in different formats: