Moore's Law is setting computers more powerful, applications on the web can fun and interesting. Althought some people might thing it's gonna be the biggest applications for computers, I believe that simulation will really elevate the meaning of human life. More and more applications in the simulation world will become easy & available with the advancement of computer progress. As of today (2007), little have been used, discovered. The problems lie in modeling the real world versus to run it in a fast simulation.
Here are some important links to learn on the simulation technology:
List of Distributed Computing Projects around the world on Wikipedia
Simulation on Future Wikia