Youtube is the best site to watch videos on the web.Downloading videos from Youtube is really simple. There are sites which allow you to download videos from Youtube without any difficulty, just by inputting video URL.
Some sites are given below:
Vixy allows downloading youtube videos in many formats. It allows you to download YouTube’s video to AVI/MOV/MP4/MP3/3GP file format online. It has very handy options to download videos in various formats required for Personal Computers, MP3 Players, iPODs and mobile phones. To download the video go to Vixy.net, enter the URL of your favorite youtube video and select the download format. Click on start to download.
This is one the easiest and my favorite site to download Youtube videos as flv files. When you are watching a video, just add the word “kiss” to the browser URL and press enter. For example if you are watching a video at youtube.com/watch?v=dXC3BFDq7U4, you need to add the word kiss in the begging of the URL[kissyoutube.com/watch?v=dXC3BFDq7U4] in your browser address bar and press enter. A link to download the video as FLV movie file. The FLV movie can be played back by many free FLV Players available on the net[Click here to download free FLV Player]