I know this might possibly be a repost, if so just delete it. My brother has been using an addon for about a year now that always gives me laughs. Basically it's an addon which you press "Stumble" on your toolbar, and it takes you to random sites. Based on what you don't and do like, it will become smarter and smarter to fit your likes/dislikes.
Official statement:
"Channel surf the internet with the StumbleUpon toolbar to find great websites, videos, photos and more based on your interests. StumbleUpon learns what you like and makes better recommendations.
Connect, Meet and Share
Connect with friends and share your discoveries, meet people that have similar interests"
Download from:
Welcome to StumbleUpon
(No direct link, just look for the download button on the right side.)
It's pretty damn fun once you use it a little, a great time waster :P
Once again, most probably already have seen this. (I searched for it so don't scold me!)
-shiny