With Central Intelligence Agency funding and guidance, bin Laden left college in 1979 to become a leader in the mujahideen fighting against the Soviets in Afghanistan. He continued to be a CIA asset throughout the Ronald Reagan Administration, at least until 1989. Bear in mind that then-Vice President Bush had been a CIA director and maintained close ties to the Agency. Regardless of whether al Qaeda exists as an organization, or a database, or in some other form, there's no question but that it was—and possibly still is—a CIA operation.
(Note: A person writing to the Huffington Post seems to have scooped me on this one because I was a bit slow in completing this article. On May 2, a writer called Nastywolf commented that he suspected that Pakistan had been keeping bin Laden under house arrest and was hoping to hold him for some opportune moment; but that the U.S. "stepped in and ruined their game." (link) The theory that the U.S. and Pakistan were doublecrossing each other in this matter is interesting indeed.)