Need Help With Guestbooks, and Comment Boxes

It has been a long time since I bothered with guestbooks, and comment boxes. Now I am looking for a program, or a site that will allow me to create a guestbook / comment box.

So for example. If some one is on my site and they want to leave a comment on that certain page all they do is type in there name, and there comment, and click submit. Bam! You see that comment appear on that page instantly. That is what I am looking for.

Here are some examples: YouTube, Chris.Pirillo.com, Geeks.Pirillo.com MTV.com, etc.

Now I tried searching on Google but still can't find the right one.

What sites or programs do you guys suggest?