The UC San Diego’s The Guardian has a good article on the Intelligent Design movement / controversy.
Intelligent design assumes that the world is so complex, that it is so statistically unlikely for humans to have formed, that God or some other higher power must have designed it. Even assuming that the two ideas are equally valid explanations of the world, evolution does not require the additional belief, a massive leap of faith, in a mystical higher power in its explanation. However, intelligent design suffers from an utter lack of positive evidence in its favor and thus is as valid of a scientific theory as the notion that a Flying Spaghetti Monster, the subject of a well-known satire of intelligent design, created the world.
Link to the article.