Information about Wantyoutube

(1) What is Wantyoutube?
Wantyoutube is a popular website to download, save, and extract Youtube  videos.

(2) Is Wantyoutube free or needs to charge anything?
Wantyoutube is free, and forever is, according to this page: Readme

(3) What are the video websites that can be resolved by Wantyoutube?
Wantyoutube supports lots of video-sharing websites such as: Youtube, Metacafe, Myspace, 5min, Break, Current, Dailymotion, Facebook,Google Video, ku6, Megavideo, Megaporn, Photobucket, Sina, Spike, Tudou, Veoh, Vimeo, Yahoo Videos, FC2, Yam, Youku, Xuite, Xvideos, 56.com (and other nearly 360 sites..)

(4) Is Wantyoutube safe to use?
It is. There are always people on it.

(5) The formats Wantyoutube is available? 
MP3, MP4, 3GP, WebM, FLV, HD Quality Movie, mobile phone, ipad, iphone, ipad, cellphone, playstation, android, Mac computer, and so on.

(6) Where is Wantyoutube?
Go to http://www.wantyoutube.com/

(7) Any tutorial to teach me how to use Wantyoutube?

Yes. 
For webpage: Readme

For video tutorial: