Download online videos without installing any software or addons

Previously  we discuss about how to download Youtube video and some softwares. If you want to download videos for other site like Google videos, Current, Facebook, Orkut and so on you want to install another software or addon. But there is no need to install any software or addon to download videos for video hosted sites. There are some free online services to download online videos by just copy and past video links in that site it will give download link in FLV, AVI and some video format files. Most of available format is FLV it is the flash format file uses to fast loading of video in website. It is better to download and install the Flash Player or VLC for playing flash videos. I selected three sites liked by me.