VDownloader is a powerful tool that can search, download and convert videos from Youtube, Google Video, Metacafe, MySpace, DailyMotion, Pornotube, Yuvutu, and many other similar sites, saving them in AVI or MPG format. It is also a powerful video converter.
It also supports HQ downloads, MP3 downloads, and much more.
It is completely FREE, which means no regristration, and this isn't a trial. It's 100% shareware. It's also safe.
I know there are alot youtube rippers out there, aswell as Mozilla addons, online youtube rippers, and much more, but none of them worked as good as this one.