How to download youTube movies?

There are many good movie clips in youTube that I would really like to keep before it becomes unavailable. Do you know how to do it?

A google search on youtube download produced 470,000,000 results, some of which should be useful.  One of my favorites was to use a bookmarklet, one click of which used to add a download link in the youTube's movie page I was watching.  Unfortunately, this bookmarklet ceased to work when youTube renovated its web site just a couple of weeks ago.

I will offer two solutions that work as of today:

• For Firefox users, install the following addon/extension
  1-Click YouTube Video Download.  Afterwards, when you watch a youTube movie, the page will have three links that allow you to download the movie in FLVMP4or 3GP formats.  
• On a PC, download and install YouTube Downloader from http://www.youtubedownload.altervista.org/http://www.youtubedownload.altervista.org/.  This stand-alone program asks you for a youTube page to download and is smart enough to get the page address as you do a copy [control-C] of the address.
  
  

I am unable to find an extension for Google Chrome that works, but I am sure it is a matter of time.