Online videos are very popular with the emergence of YouTube, Google Video, or many others. May be we are all likes to download these videos and takes different method to download.
Here is a lists online video downloader

YouTubeX - YouTubeX.com allows you to save and download YouTube videos easily using only your IE or Firefox browser. It also supports Myspace Video, Ifilm, and Metacafe etc.

Flvix - You can convert and download videos from You Tube, Google Video or directly from .FLV file.

VideoDL –It is a quick AJAX application that allows you to download online video into your computer

Video Downloader – Available as a Firefox and IE extension

Kcoolonline – From this site you can download videos from more than 98 sites

Vconverter - allows you convert and download online video like YouTube to more popular formats like wmv, mov, mp4, mp3, 3gp etc.

MediaConverter – Allows converting videos from YouTube.

KissYouTube - A service that provides an effective ways to download videos from YouTube. Download speed and response rate is quick.

KeepVid - Download and convert videos from YouTube, Google Video, MySpace, DailyMotion, Blip.tv, etc.

Vixy – Convert and download videos from YouTube and other popular video sharing site.

DownThisVideo - lets you download videos from YouTube, GoogleVideo, MetaCafe, and others.

YouTubeDownloads – Download and save movies from YouTube