Quickly download YouTube videos

I recently wanted to keep a video from Youtube for my personal archives. After a quick Google search, I stumbled upon a simple yet efficient site called KeepVid. By going to this site and pasting the URI of the Youtube video (or a few other services) that you want to keep, you will get a download link to get the file in a nice high quality format. Simple, elegant, and very useful. From what I can see, they mainly make their money from the ads.