I feel so naughty, telling people how to copy material that belongs to others, but sites like Youtube and Google make millions from videos that don't belong to them anyway (people voluntarily submit them free). I don't encourage the downloading of copyrighted materials though, unless there is no affordable, commercial option. So here are some programs I found to help out.

A webpage that lists the 23 most recommended options, including websites that convert the files for you, to installing your own programs to do it yourself. (it mentions V-downloader, but I found it to be an awkward program that often was never able to access the video files anyway - unless it has been upgraded since I installed it)
http://mashable.com/2007/05/05/download-youtube-video

Mozilla Firefox. It was recommended to me by another board member some time ago, but I found that you need an extension to the browser for it to be able to do it. And here's how:
http://www.gilsmethod.com/htdownload...romtheinternet

And one Website that does it for you, that appeared on a number of searches (could be reliable, but haven't tried it for sure).
http://www.savetube.com/
If anyone else here has any recommended options or programs, post here.