The recent revelations of how much our privacy is being invaded have moved Dewald Pretorius (the owner of SocialOomph.com) to make available a gratis encryption service that everyone can use. It does not cost any money, it is very easy to use, plus it's completely anonymous (no need to create an account).
In a nutshell, you use the free site to encrypt text you want to protect, paste the encrypted text into an email, tweet, Facebook post, Google+ post, etc., and give the decryption password to the intended recipient. The recipient uses the site to decrypt the text using the password you chose (only someone who knows the password can decrypt it).
It's extremely simple to use. Nothing to install and nothing to configure. As the name suggests, is free and always will be.