This is a game which has cropped up in the computer lab of my school. Ideally you should have 5 or more players, but it can technically be played with 2 or more. The game is simple, but addictive.
To start one player calls out a word. Everyone playing hits the random article button on Wikipedia and trys to get to the word chosen while only using internal links to other wikipedia articles. This game can go very quickly or take awhile depending on the word and the article you start with. Nevertheless when every worthwhile site is blocked the game is addictive indeed.