There are tons of websites that let you save YouTube videos, but KissYouTube might make it even easier.
When you see a video you’d like to save, all you have to do is insert kiss in front of the YouTube URL, i.e. http://www.kissyoutube.com/watch?v=tRTk0RPXtW4
You could also enter the YouTube URL in the form on the KissYouTube homepage and get a link to download the .flv file.
You’ll need a .flv capable player to view the file on your computer. KissYouTube lists a few .flv players and if you don’t want the .flv format there are some converters listed as well.