Springfield, Vermont, winner of the Springfield Challenge with 15, 367 votes, hosted the world premiere of The Simpsons Movie on Saturday, July 21, 2007.
Matt Groening and the Simpson family were in attendance.
For more information, a quick search turns up plenty of news stories, photos, and videos of the event.
However, I have yet to find a photo of any "Duff & D'oh-Nuts," the beer-and-donut-flavored ice cream created by Ben & Jerry's for the movie premiere. It was available for one day only, and only in Springfield.