Watch the beginning of the end of the world as the first beam circulates in the Large Hadron Collider LIVE September 10 (from 9:00 to 18:00 CEST) at CERN's website: clicky
Of course, there will be no danger of spontaneous black hole formation or sudden presence of Combine shock troops because they won't actually start the smashy-smashy until later this year and the facility is not located at Black Mesa. This is just a preliminary lap, a warm-up. Physicists hope that by colliding ever smaller particles with enormous amounts of energy they'll find the Higg's Boson, or top quark, the particle that (we think) imparts mass to other particles and that sounds like the name of someone in a horizontally-striped shirt with a parrot on his shoulder. A secondary goal is to provide employment for physicists everywhere, as well as giving them a sweet place to crash while they're in Switzerland. (See whut I did thar?)
Edited 9/09/08 to correct description of Higg's boson.