I think I should contribute something from the "strategic" point of view to the "what now?" discussion since it seems to be sadly missing, or, perhaps, simply obvious to all.
1. Terrorism is a military strategy to accomplish certain specific goals. It is used by those whose numbers and strength is unquestionable less than their opponents. It can be remarkably successful. The French reign of terror was conducted by 22 men and successfully control an entire country.
1. The specific strategy of the terrorist is to provoke a response in the enemy that leads to the enemy's downfall. It is warfare's equivalent to jujitzu in which the small in number and weak in strength use the opponents strength against him.
As one example, the Algeria terrorist provoked the French to withdraw from Algeria all native-born troops (and other actions) that clearly demonstrating to Algerians that the French did not really consider Algerians equal citizens and Algeria, itself, a southern province of France.
3. It is clear from his statements that bin Laden wants to provoke an attack by the US-led Western forces that will be viewed by the Moslem world as an attack on it in order to start a war which he believes the Moslems would win. It is not that he wants to weaken us directly, although the economy has taken a hit, he wants to provoke us to act in a way that will support his assertions about our animosity toward Islam.
4. Terrorists have been halted repeatedly when their actions produce either no response or responses that they do not want. The Palestinian terrorists instantly stopped hijacking planes and attacking airports following the Athens attack when the response in countries like Greece was unfavorable. In fact, Arafat issued a death threat to any such hijackers.
What now? This is a no-brainer. We must respond in a way that disqualifies bin Laden's goal. We must respond in a way that indicates that we are not hostile to Islam. Everything else, is commentary, as the saying goes.
5. Unfortunately the structural problem lies in the fact that information is capable of being distorted. No matter what we do, many people will be told we have done something else. Thus the terrorist does not really have to provoke us into an act that will be useful to him, but he has to be able to interpret what we do in that fashion. An example is that the attack on the World Trade Center is being reported as the work of the Israeli secret service. What scientists can do now is perfect systems that allow open communications. What ever happened to the sun-powered computers that could be provided to third world people that got information from satellites?