StumbleUpon

Here's a tool that will let you find interesting websites with no effort at all. After you download this toolbar (which supports Firefox on Windows, Linux and MacOS, as well as Internet Explorer), and select topics of interest for you, you just click "Stumble!" to get a random interesting web site. By clicking "I like it!" on web pages you like, you refine StumbleUpon's understanding of your interests, while also recommending the site to others. See their about page for more information.