Terrorism is a symptom; fight the disease
Around five thousand people have lost their lives. Anxiousness is forcing the search for answers to be quick and the reponse swift. Who did this? Where are they hiding? How soon can we strike? All valid questions, of course, but their answers will do little to help prevent future similiar disasters.
Terrorism is a symptom of a complicated disease. Desperation, cult-like brainwashing (using religion as a tool), and misguided patronism are some of the agents acting to further this disease. Focusing all our wrath on a single element, like the religion of Islam, is short-sighted.
As long as the people of the middle-east, or anywhere else for that matter, continue to live in an under-developed society filled with poverty, war, and ruled by caliphs they'll be a breeding ground for the kind of people who comitted these hideous acts.
Terrorists are products of their environment. Where they given equal opportunities they would likely turn out just like you and me.
Look at the history of the world. Most civilizations have at a point in their development been just as cruel and inhuman. We've developed beyond that thanks to higher standards of living, peace, education, and many other such factors. We must help others do the same.
Dealing with the responsible behind this will feed our craving for revenge and ease the feeling of powerlessness, but won't cure the disease.