Google has a nifty new Firefox extension out called Blogger Web Comments.
In a nutshell, imagine a browser plug-in that automatically does a Technorati search for every page you visit, popping up the results (if you like) in a little balloon. That's basically what Blogger Web Comments is. Here's a screen cap of what it returns:

But, if you're also a user of the Blogger blogging site, then Blogger Web Comments does something extra: it allows you to post a blog entry about the page you're looking at with just a single click (and then typing whatever it is you wanted to say about it).
Nifty...and as always with Google, the price is right. Go check it out.