ClipNabber :This web service allow users to download videos from youtube etc. you can do it by simply pasting address link in it , it will generate a link which you can download videos .
you will need a flv player inorder to play this video,or you can convert it later by using any converting softwares.it is fast and very easy to use.
Vixy.net: is another site that not only downloads online videos, but it will also convert them to AVI, MOV, MP4, 3GP, or MP3 (if you want to extract
the audio from the file) etc. Using this site, you don’t have to worry about downloading a FLV player as you can convert it to Windows format.
KeepVid also supports just about any video sharing site out there and the only difference about this site is that it also has a Top Videos section, so you can quickly download the most watched videos around the web.you need java plugins for using this in your device
DownThisVideo has a nice tag cloud at the top that you can click on to find videos quickly. From what I could tell, this site is mostly used by Japanese because the popular videos are mostly Anime, etc. However, you can still use it to download any YouTube video
This is the best service that I ever experienced fast and you can download in what ever the format that you like ,even in different resolution , and you can use this by simply
pasting the link on the savefrom website or on watching video on youtube go to address bar and remove ”http:\www” and type “ss” without quotes then it will redirect to savefrom page and by just clicking on download links to several formats and resolution will observe by simply clicking on them downloading will start . and you can even use this service from your mobile phone .it supports many website