It’s really easy… just bring up the YouTube page that has the video you want to keep, and copy the URL of the page. Next, go to keepvid.com, and paste the url into the text field at the top of the page. KeepVid will give you a link to download the Flash video file.
Now, here’s where you need another piece of software. The .flv file that you’ll download from KeepVid isn’t much good, because most players won’t play it. You need to convert it into another format. Being on a Mac, I use the free utility, iSquint. It converts the .flv file into an iPod-ready Mpeg. If you’re on a PC… well, I don’t know what you should use, sorry. I don’t keep track of PC software. Maybe you should buy a Mac.
Two side-notes… KeepVid works with a lot of sites, not just YouTube. And, if you end up liking iSquint, you should donate, to keep it’s development alive.