Here is how to download clips from Youtube to use however you like.
Step 1: Download the File
To download the video you want you may have to use a site to get the flash file (or whatever type of file format the video is in). A good and easy site for Youtube videos is http://www.techcrunch.com/get-youtube-movie/.
Note: You may need to rename your video file to a .flv after downloading it.
Step 2: Convert the File
Use a conversion site such as http://media-convert.com/convert/ to upload and convert you file to .avi, .wmv, or any other format you need.