Breitbart.com has an article about the Top 10 April Fools hoaxes and it makes great reading. The hoaxes were ranked on numerous criteria including number of people duped, by the San Diego Museum of Hoaxes.

One of my favorites:

In 1996, American fast-food chain Taco Bell announced that it had bought Philadelphia’s Liberty Bell, a historic symbol of American independence, from the federal government and was renaming it the Taco Liberty Bell.

Outraged citizens called to express their anger before Taco Bell revealed the hoax. Then-White House press secretary Mike McCurry was asked about the sale and said the Lincoln Memorial in Washington had also been sold and was to be renamed the Ford Lincoln Mercury Memorial after the automotive giant.

I found out about the article on doggdot.us which is an aggregator that blends news from Slashdot, Digg and Del.icio.us.