Click for Freedom. If somebody along the way looks at the mail they can't understand it. But they do know you are sending encrypted mail to your pal.
Encryption is even illegal in some places.
There is tons of spam flying around the Internet. Most people can't delete it fast enough. It's virtually invisible. This site gives you access to a program that will encrypt a short message into spam. Basically, the sentences it outputs vary depending on the message you are encoding.