Here are some from this year.
The Guardian drops print edition to publish via Twitter
Econoland-a new theme park
A new breed of tartan sheep
Mountain Cleaners in Switzerland
Flying Penguins was from 2008
A round-up of recent years is at the Guardian and at April Fools Day on the Web.
Here is the video of perhaps the most famous April Fool gag of all--the 1957 Spaghetti Harvest from BBC