I've run across several world's fair stories recently.
Various American Cities 1933-1940:
The National Building Museum will host an exhibit entitled "Designing Tomorrow: America’s World’s Fairs of the 1930s." It opens in October 2009.
New York 1939-1940:
The New York Times has an interesting article about a bomb that killed two city detectives in the British Pavilion. The case remains unsolved.
Seattle 1962:
The monorail from Seattle's 1962 Century 21 Exposition will soon be returned to its original condition.
New York 1964-1965:
I had no idea that pita bread was introduce to the United States at the 1964-'65 New York World's Fair.
Spokane 1974:
The Seattle Times writes about Spokane's Riverfront Park, legacy site of Expo 74.
Man Belongs to the Earth, a film from the United States Pavilion is available on YouTube. It's an early example of environmentalist messaging from the first world's fair with an environmental theme.
Shanghai 2010:
France has set up it's Expo 2010 pavilion web site .
(Unknown) 2020:
Copenhagen might bid for Expo 2020.
The Gotthard Region of Switzerland might also bid for Expo 2020.