http://www.impossiblestory.com
http://www.getthemessage.net
Have a look at these 2 viral campaigns, worked on by my mate Des at Glue. For the Royal Navy one I advise you to put in the most flippant message you can think of, makes it so much more amusing.
To see an example of a truly important message that the Royal Navy might use helicopters for click here, feel free to reply with the most imaginative thing you can think of.