clipgrab (downloading video tool)

ClipGrab is a GPLv3-licensed Open Source project and of course
also available for Linux.

ClipGrab is a free downloader and converter for YouTube, Vimeo,
Metacafe, Dailymotion and many other online video sites, see
more in: http://clipgrab.org/faqs/supported-sites

It converts downloaded videos to MPEG4, MP3 or other formats
in just one easy step.