Firefox add-on: Download Flash and Video is a very nice add-on.
Once you installed the add-on, you will see a downward arrow on the lower-right side of the browser window. If you are on a web page, clicking on the arrow will show a list of flash sources on the page. If you mouse over an item, the source on the web page will be highlighted. You can save the .swf file directly or you can start the video and re-click the arrow to download the .flv files.
Once you have the video saved, you will need a player to view the video.