Has your paranoia about government snooping ratcheted up lately with all the revelations of NSA spying in its Prism program? If so, Amit Agarwal shows you how to use Google Docs to do very strong encryption to encode those messages.
How to Encrypt your Gmail Messages with Google Docs
There are a couple of browser extensions that help you encrypt Gmail but here we discuss a new and more simple Google Docs based encryption method that works across all browsers and requires no add-ons or apps. You secure your message with a strong password and the recipient will have to enter the same password in order to decrypt your message.
Agarwal has very clear video and text instructions here. I highly recommend his blog and newsletter for excellent advice.