Also in the category of "funny April Fool's Day jokes" would be Kingdom of Loathing making a joke familiar based on a retarded HAL 9000. Livejournal saying that they'll be offering a graphic of an upraised middle finger as a virtual gift.
Here is a not-funny April Fool's Day joke: lying to people and then mocking them when they believe you.
No holiday should be an excuse to hurt or humiliate people. Ever. Not if you think they deserve it, not if you think it's funny. It isn't funny to make someone feel stupid for trusting other people. It isn't funny to make them worried, upset, or concerned over a lie. It isn't funny to use lies to hurt people and then hiding behind the date as a shield.
April Fool's Day should be about pretending to make a fool out of yourself, not making fools out of other people.
Edit: I guess what I'm trying to say is, if anyone reads this and still feels the need to post, "omg my mother died! ;_;" *waits for people to offer condolences* "teehee april fool's you silly people!!" ...well, I need to prune my friendslist anyway!