StumbleUpon is an intelligent browsing tool for sharing and discovering great websites. As you click Stumble!, you'll get high-quality pages matched to your personal preferences. These pages have been explicitly recommended (rated I like it) by friends and other SU members with similar interests. Rating these sites shares them with your friends and peers ? you will automatically 'stumble upon' each others favorites sites.
Here are some cool sites I find suring my stumbles this afternoon: