TechCrunch YouTube Video Download Tool
You just need to enter the YouTube URL of the video and the tool will automatically download the video to your computer. The video is saved as a FLV file or Flash Video file on your computer. You will need a FLV media player to play the videos. A Free FLV player is available at Download.com
Another place where you can find a YouTube Video Download Tool is DownloadYouTubeVideos.com. Here too you will need an FLV media player to play back the downloaded YouTube videos.
YouTubeX is another good online tool which lets you save YouTube videos to your computer. Again, you will need a FLV player to play the saved YouTube videos.