National Geographic on Swarm Theory -- the field variously known as "complex systems", "emergent behavior", etc. In some sense certain complex systems are greater than the sum of their parts -- an ant colony seems to have some sort of "intelligence", even though a single ant doesn't. Each individual person betting on a horse race has their biases, but in parimutuel betting the final odds (which depend on how many people bet on each horse) very nearly reflect what actually happens. Juries are smarter than each of their individual members -- although only when the jurors act independently. (This makes me wonder: are people better or worse at following complex arguments than they were a couple hundred years ago?)
Public transportation systems, especially in the U.S., are notoriously inefficient; I suspect a large part of this is because they run on the same routes they've historically run on. I have to wonder if this sort of thing could be applied to redesign of public transit; the article mentions other logistical applications. Southwest Airlines, for example, has used this for scheduling. And American Air Liquide, which delivers gases made at a large number of plants to a large number of customers, has redone a lot of their delivery this way.
Unfortunately, though, Air Liquide has found that some of their drivers have to do unintuitive things -- they're no longer delivering from the plant nearest the customer to the customer. I have a feeling this wouldn't work well with people; you can't tell someone "well, it's going to take you an extra half-hour to get to work today, but that saves fifty other people one minute!" even though it does reduce total transit time.
I suspect there might be applications to, say, the dispatching of cabs, or the placing of shared cars (disclaimer: I am not a member of Philly Car Share but lots of people I know are). Or to a hypothetical company like the one Scott Adams suggested which would get people rides by having them text-message their destination to some central server and then hook them up with someone who's willing to give them a ride. Although the appropriate metaphor in this situation is actually more like traditional, decentralized hitchhiking. Hey, maybe that's the solution to the energy crisis!