Robin Good: VDownloader is a free Windows sooftware that allows you to download a copy of your favorite videos from YouTube, Hulu, Vevo and other sites.
VDownloader acts also as a good FLV and MP4 video player.
No registration required.
Free to use.
N.B.: You may also want to try out www.wontube.com where you can search for any video and download it immediately straight from the web.