Mozilla Firefox has plenty of really useful add-ons and 1-click YouTube video downloader is one of them.
Download the latest version from here which works with the new YouTube code (some previous YouTube downloader add-ons in Firefox have stopped working or have glitches after the site was changed).
Select Add to Firefox to get it installed.
Once the add-on is installed,verify by going to Tools >Add-ons in Firefox.
Go to any site with you tube video content and now you will notice a small link indicating the format in which you want to save the you tube video (FLV/MP4/3GP/HD).
Click on the required format and let the download begin in Firefox.
Enjoy.
>I had been using FastYouTube downloader and it had stopped working.
Thanks a bunch for this newer addon.
>@ Joanne
Yes,the upgrade to YouTube site broke many video downloaders.