StumbleUpon Reviews - 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. In effect, StumbleUpon’s members collectively share the best sites on the web. You can share any site by simply clicking I like it. This passes the page on to friends and like-minded people – letting them “stumble upon” all the great sites you discover.