ClipGrab is a free downloader and converter for YouTube, Vimeo, Metacafe, Dailymotion and many other online video sites . It converts downloaded videos to MPEG4, MP3 or other formats in just one easy step.
ClipGrab is a multi-platform software for downloading videos from popular websites such as YouTube , Vimeo , Dailymotion or Metacafe . It also provides the possibility to convert the downloaded files to other file formats such as MP3 , MPEG4 , OGG Theora or WMV . It is published as free software under the terms of version 3 of the GNU General Public License . 
ClipGrab downloads and converts Internet videos with ease and offers more features than most other YouTube downloaders. It doesn't download very quickly, though, and the video and audio quality won't be the ideal. However, if you need a program that downloads videos automatically, you might want this one.
People often want to download online videos from sites like YouTube to watch offline or edit. ClipGrab for Mac claims to allow users to save Internet videos to their desktop, but ultimately doesn't deliver.
Use the command line to quickly download videos from YouTube, Vimeo, Ted, Discovery and over 40 other sites using one simple program. It’s called MovGrab and it’s a great, free program for Linux.