Sothink Web Video Downloader for Firefox is a simple, clean and free Firefox extension for you to capture video, download video and save video from YouTube, Google, MSN and almost all popular video sites. You can use this video download tool to download embedded Flash videos and direct Flash video content in different formats including flv, wmv, asf, avi, mov, rm and rmvb. It also lets you download Flash SWF files like Flash games, Flash cards and presentation, etc from Internet at the same time. And now you can run it under WINDOWS, LINUX, Mac OS X (x86), or Mac OS X (PPC).
But a word of warning, it does take a lot of time, and it depends how good your network connection is. on the wireless, it's a killer. It works better at their home.