Stumble Upon

I'm addicted. I found the Stumble Upon toolbar add-in for FireFox, and I'm hooked.
Haven't seen it? When signing up you select a range of websites in different categories, such as Activism, Science, Philosophy, etc. Clicking on the Stumble button that's now embedded in your Firefox toolbar takes you to a site randomly selected from your lists. If you see a site you like while browsing, you can click the "I like it!" button, tell Stumble Upon a bit about it, and add it to a category for others to see. Likewise, you can vote thumbs down on a site.
I've Stumbled Upon an amazing array of things, from Libertarian Quotes to a Reporter's Desktop to instructions for building a true to scale Solar System Model, complete with spreadsheets.
Granted, many of the sites fall under the whimsical category, and occasionally you wonder why in the world other people liked a site. But for the most part, Stumble Upon provides a fascinating glimpse into the Web that really hasn't been available for years. It a truely democratic web catalog, and it works.