Intelligent Design is arguably one of the stupidest concepts ever conceived by man after young-earth creationism, the Flat Earth Society and original sin. It was either created by a complete idiot, or by a person who thought that making thousands of sub-intelligent people look foolish would be a fun idea.
Advocates of intelligent design argue that it is a "scientific" theory, and seek to fundamentally redefine science to accept supernatural explanations . However, ID is at best a way of explaining what we don't yet know by saying god did it, but as that has no valid data or provable hypothesis it is in no way scientific. Even theists like Kenneth Miller state that this is a faith position and has no place in a science class. ID has the potential to block scientific research into understanding what we don't know. People who have made discoveries in the past that have challenge faith positions have only been able to do so by not allowing religion to cloud their judgment.
Basically, ID appeals to people who don't have the intelligence to understand how evolution works, but find satisfaction in the idea that God created everything with magic powers. The folks who believe it tend to be stupid and Ape-like. This ironicly provides indirect evidence that Humans descend from apes.
Intelligent Design in a Nutshell
Take the following article - Creationism - and replace the word "God" in each instance with the term "an intelligent designer of some sort". And that's it. Really.
Here is an example:
"Cdesign proponentsists believe that one day an intelligent designer of some sort was in his room playing with his toys. Then he got out his Play-Doh and made a blue ball. He put some more Play-Doh of different colors onto the blue Play-Doh ball, thus creating the land and the sea. Furthermore, an intelligent designer of some sort took all his little action figures and placed them about on the Playdoh, creating the Earth's animals. Finally, he took his Ken doll and thus created Adam." (Creationism)
Charles Darwin originally thought out the idea of Natural selection. Since then, scientists have developed the concept of natural selection further and are on the way to explaining the origin of life as well as the gradual development of complex life.