Windows/Mac/Linux: Google Sidewiki is a new browser plug-in that adds a universal commenting system to the web, allowing users to comment and read other people's comments on any page on the internet. It's not a new idea, but, well, it's Google.
Sidewiki installs alongside the Google Toolbar, so it works with both Internet Explorer and Firefox. Google also says that they're "working on making it available in Google Chrome and elsewhere too". (Hopefully they'll make it an extension for Chrome, too, rather than forcing it down user's throats.)
After you install Google Toolbar with Sidewiki and restart your browser, you'll end up on a landing page that illustrates how the tool works and encourages you to write your first entry. (Incidentally, when you comment on a page using Sidewiki, that comment will show up in your Google Profile page as well — like this.) Comments on the internet aren't exactly known for their quality (Google-owned YouTube is notorious for having some of the worst, most inane comments on the internet), but Google's aiming to address that with Sidewiki:
We worked hard from the beginning to figure out which [entries]should appear on top and how to best order them. So instead of displaying the most recent entries first, we rank Sidewiki entries using an algorithm that promotes the most useful, high-quality entries. It takes into account feedback from you and other users, previous entries made by the same author and many other signals we developed.
The universal comment system isn't new by any means, but if anyone's popular enough to get more widespread adoption for the idea, it's Google.
Bundling Sidewiki with Google Toolbar is strike one in my book, but I've never liked clunky toolbars and never really understood why I'd want to install Google Toolbar in the first place. Some people obviously like the toolbar though, and for others, maybe Sidewiki is reason enough to install it. Google Toolbar with Sidewiki is a free download for Internet Explorer or Firefox. If you give it a try, let's hear what you think in the comments.