There's probably an official website somewhere, but I saw the press releases reprinted on cartoonist John Kovalic's blog:

Paizo Publishing has announced that Dragon and Dungeon magazines, which they publish on a license from Wizards of the Coast, will end with the September 2007 issues, numbers 359 and 150, respectively. Paizo's license with Wizards expires at that point. Wizards will thereafter "be moving the kind of content currently found in Dragon and Dungeon to an online model," said model unspecified at this point.

Paizo was the publisher of the most recent incarnation of Amazing Stories, which ended more than a year ago for reasons that sound similar.