I’m a HUGE stumble fan. This is how StumbleUpon Team describes it. “Surf the internet with the StumbleUpon toolbar to find great websites, videos, photos and more based on your interests. StumbleUpon learns what you like and makes better recommendations. Connect with friends and share your discoveries, meet people that have similar interests, and check out what other people are discovering.”
StumbleUpon is a web browser plugin that allows you to discover and rate webpages, photos, videos, and any thing on the web. These webpages are shown when you — known as a Stumbler — click the “Stumble!” button on the toolbar. StumbleUpon chooses which new webpage to display based on the your ratings of previous pages, ratings by your friends, and by the ratings of users with similar interests. i.e. it is a recommendation system which uses social networking principles. You can rate, or choose not to rate, any webpage with a thumbs up or thumbs down. Toolbar is available for Firefox and Internet Explorer.
You must give it a try, I am sure you will not think about un-installing it.
StumbleUpon can be used to effectively increase traffic if you only knew how to use it. Here are few useful links.