Most of the bloggers out there know about Digg, Reddit, Furl and many more. They are social networking sites that allow you to submit interesting stories or webpages. Other reader can then, “vote” for these topics making them popular. They also allow you to add other users with similar interests as friends.
You can then click the Stumble button on the toolbar to visit sites which are similar to your own interests. This is the unique feature in StumbleUpon, instead of searching for some topic to read, on a search engine, stumbling takes you to websites based on your interests and preferences. There are nearly 500 topics which users can choose from to indicate their interests and preferences.
I have been stumbling for a few months now, but yesterday a user submitted my blog to stumbleupon. You can see the increase in traffic on the image below. The main difference I noticed between Digg and SU is that SU provides a constant stream of traffic once your blog has been reviewed.