Date

The first thing I do every April 1st is go to Google's homepage and look for what they did. This year it's Google Romance. Last year it was Google Moon, which is actually useful until you zoom in all the way - or maybe it was for the moon landing anniversary last year, I forget. But it's an extension of the Google Copernicus project. And the Google Mars project is more serious.

(One of the Romance pages also lists the Pigeonrank and Mentalplex past April Fool's projects.)