http://www.stumbleupon.com/

StumbleUpon is a popular plugin for your web browser (with toolbars for Firefox and Internet Explorer) that’s helps you discover great new websites, videos, articles and more from around the web. The main feature of StumbleUpon is the Stumble button, when you click this it’s like channel surfing the web, bringing up a new page that other StumbleUpon users have liked and added. You can try out the demo on StumbleUpon.com before you sign up so you can see how it works.

You can give any site you’re on a thumbs up or a thumbs down using the toolbar and StumbleUpon will remember the kind of sites you like and show you more of them in the future, and vice versa with the kind of pages you don’t like. You can even add your own pages to StumbleUpon to share with other users. Even StuffToGet is on StumbleUpon so if you want to discover some great new things to see while surfing the Internet, sign up and start stumbling!