In 2002 BBC break a story about German scientists discovered that blond hair would disappear in the next few centuries as far as there is a recessive trait. Almost a year later the New York Times aired a report that the findings had been faked but the study has still been cited up to 10 years in various sources.
In 2000 a university student at MIT created a website with instructions on how to grow a kitten in a jar so that it assume the shape of the container as the bonsai plant. Despite of the fact that it was very ironic, after criticism from animal rights groups, MIT had to remove the website.
The 1938 radio program voiced by Orson Welles caused the most widespread panic in the history. Although it wasn't intended to scare people into believing the world was really under attack by Martians, as long as the program was delivered in a series of fictional news bulletins, many people believed it was true. Some even declared to see flashes and smell poison gas.
Most people aren't familiar with chemical nomenclature and associate dihydrogen monoxide with something poisonous. However, it's just water. So, in recent years when various emails have circulated highlighting various warnings associated with dihydrogen monoxide they have managed to generate quite a scare among people.
The Archaeoraptor was what scientists claimed to be the link between birds and theropods ( a group of saurischian dinosaurs) in the fossil record. Although many archaeologists had their suspicions it wasn't until later on that it was proven to be fake.