Auto Generate a Page Description

Is there any easy way to generate a description for a web page? Any way that I can think of that would come anywhere near giving a decent description would take a while to program.

So, I’m wondering if there is a library available to do this. And, if there isn’t, does anyone know of an efficient way to do this?

It doesn’t have to be as good as Google’s. I just need something that can give a decent description of a web page.