I'll have to make this a shameless plug, but it's probably the only way any of you will get to know about this.
My startup, Qaym.com is a restaurant rating site in Arabic. We're located in Saudi Arabia. April fools isn't a big thing here or in the Arab world in general. But people know the concept. Today we announced that we're changing the site to become exclusively a camel rating site.
We even made a logo: http://blog.qaym.com/2010/04/blog-post.html
And a homepage to boost: http://www.qaym.com/
Most people got it off the bat. Many were confused. And a couple were actually upset, even after they've figured out it was a joke!