Zamzar is a free online file conversion utility.  What is fabulous about it is that you can use it to grab YouTube videos and save them to your flash drive.  Also nice is that you don't have to stay on the page and wait for your file to be converted, Zamzar will send you an email when your file is ready!  This is especially useful for school where it is asked that you do not stream videos during the school day.  

To use Zamzar

1. Go to http://zamzar.com
2. Click on the Download Videos tab
3. Paste in the link to the YouTube video (it will also download some other streaming video files, but not all - just try to see if it will convert the one you need)
4. Choose the format you would like to convert it into (usually MP4 works well)
5. Enter your email
6. Click convert
7. The file will be converted and a link will be sent to your email (usually within 1 or 2 hours).  You will then click on the link and be able to download the file.