Hide Your Data With A Fake Phone Jack
instructables.com
instructables.com
Sorry, couldn't resist.
p.s. Isn't there a rule about linking to the original source? http://www.instructables.com/id/Hidden_USB_Storage/
Also, you might want to encrypt the data too.
If only someone had invented a way to securely transfer data from one computer to another without the need to transfer physical media. Now, that would be a game-changing invention, I tell you. Probably a startup or seven in that idea...