“Start by asking yourself this question: assume you had a worldwide network of computers running a single application, in constant communication. What old problems could this new resource solve? What new applications can one imagine? What improvements to these existing infrastructures are required?”

Then go to here.

Just as the turn of the 20th century ushered in a new era in physics with the discovery of quantum mechanics, the turn of the millenium ushered in a new era of information technology with the emergence of wide-area collaborative computing platforms: the Grid and PlanetLab, to name two. Pure peer-to-peer systems such as Alan Kay’s Croquet wide-area operating system (formerly known as Tea) are also emerging. New applications which uniquely exploit these platforms have begun to appear:
* Education
* Wide-area collaboration
* Collaborative media, particularly in the humanities
* wide-area sensing applications in the sciences ….