CNet has an article about April Fool's Day hoaxes on the internet. It has some interesting info in it, but surprisingly it makes two rather large errors. First of all, it describes the Microsoft iLoo (an internet-enabled portable toilet) from 2003 as an April Fool's Day hoax. Microsoft announced the iLoo on April 30, making it a real stretch to describe it as an April Fool's Day hoax. But more importantly, although Microsoft did initially say the iLoo was a hoax, it later changed its mind and admitted that it was a real project. And that was the final word from them about it.

The article also describes a story that ran in the BBC last year about Cold war bombs being warmed by chickens as a hoax. I believe that's wrong. The story was odd, but true. Although when it ran a lot of people suspected it to be a joke. Wikipedia correctly lists the story as genuine but widely interpreted as an April Fools joke.