A cool plugin that I came across by chance, while searching for video download softwares. I was previously using downloadhelper - a firefox plugin, but for some reason it was not working fine on my computer.
Apart from popular video sites, Ant Video Downloader helps you to download videos from unfamiliar video sites, social networks, articles, blogs and practically any site.
You don't need to ever copy and paste the video site url to download the video. Once the software is downloaded to your computer, you would see a small icon on your status bar as shown in the image above. Whenever the software detects a video site, the download icon starts blinking and you just have to click it, to download and save the video to your computer.