Stumble Upon - Channel Surf the Internet
If I recall the story right, Stumble Upon was built by a couple of straight out of college friends. Shortly after they got acquired for a rumoured sum of 75 million dollars. Not bad for your first gig out of college eh!
So what is SU? Well you download a toolbar for your browser (Internet Explorer, Firefox etc) and you optionally tell SU what your interests are, e.g. business, gaming, videos etc. Each time you click on a button in the toolbar, SU loads a site that other people have submitted and rated. It tries to do this to match your taste, so it is good to tell it what you like.
You also get a couple of buttons to rate a site up or down. You can also use the rate-up (“I Like”) button to submit a site to SU.
Why is it useful? Well, in some ways SU can be an alternative to search and is useful for researching topics of interest. Unlike search, you are getting sites that actual people have recommended and rated highly. As you can probably imagine, SU is therefore useful for promoting websites.
Last but not least, SU is good for entertainment. If you are bored, you can just keep clicking to see what it recommends - just like flicking through the channels on your TV. Oh and what a great name Stumble Upon is by the way - very catch since many people use the phrase everyday anyway.
