Wanna download all the videos in YouTube and other sites ?
Then get Mozilla Firefox
and download the VideoDownloader plugin.Just search from google and u will find.
Next goto http://keepvid.com
Here u will find a green box.Copy the link of the You Tube video and paste.Then download.Note:When looking for save location change extension into .flv
You will need FLV Player to view.Available for download from keepvid too!