Here is a Techbyte. I have been teaching classes at a local Technical Institute, and I needed to show some Youtube videos about certain topics. But the Institute locks down the Internet in the classroom - go figure, anyway, I needed to figure it out. I found this site: KeepVid to be the answer for me.
1. Find the Youtube video.
2. Copy the URL
3. Go to the site and put the URL in the URL field just below their banner and click the download button.
4. Look where it says "Links found" under "Download Links" Green banner.
5. If found, then just click the format you want to download it.
One thing I found is that a lot of the videos are poor in resolution, but that is the nature of a lot of the videos I have been getting. They just don't scale well in a bigger screen. But, they work for my purpose.