Best software is the Internet Download Manger, The things it can do is really amazing , which includes youtube AND other embedded video downloads.
Just integrate the software with your browser and you are good to go. When you go to the youtube page, a link will appear on the player to download the video. Alternatively if you right click in the page, the menu will have an IDM component and that will give all the links(Youtube or otherwise) stored in the cache.
There are many other things you can do with IDM. However it is not a free tool. But there are plenty of Pirate versions lying around. Try a torrent search.
I highly recommend this software.