If you are a blogger, or just addicted to surfing the web, you must have heard of StumbleUpon. StumbleUpon is basically a social bookmarking application in the form of a downloadable browser toolbar that let’s users find popular sites in in various categories and by using specific tags.

As you click Stumble!, we deliver high-quality pages matched to your personal preferences. These pages have been explicitly recommended by your friends or one of 1,522,283 other websurfers with interests similar to you.

According to TechCrunch, StumbleUpon may be up for sale for $50 million.