YouTube Video Downloader

you say you don't want to install anything but theres a brill extension for safari, firefox, etc. try this;

http://kwizzu.com/

Hi

I just found this video on how to download videos from youtube with Safari 6 without any extensions

http://www.youtube.com/watch?v=KO3ABRuRyRk

To activate the developer menu you don't have to use the terminal (like in the linked video). Just go to Safari settings --> advanced --> show developer in menu bar (maybe the exact spelling is different in English...)

I use http://keepvid.com