Now more than ever, people are concerned about safeguarding their emails from prying eyes. SecureGmail by Streak is an incredibly easy to use and open source Chrome extension that adds email encryption to Gmail.
All you need to do to use it is install the extension. Then whenever you want to send an encrypted email, click on the new lock icon next to the Compose button. Compose your message as usual, and when you hit the Send Encrypted button, you'll be prompted for a password to secure the message.
To decrypt the email, your recipient will also need the Secure Gmail extension installed, as well as the password. You can provide a password hint to help that person figure it out.
Encryption and decryption happens on your local system, so Google and anyone else can't read the emails unless they have the password. Also, emails saved in Gmail stay in their encrypted form (i.e., each time the email is opened you have to enter the password to read it).
The downside, besides your recipient needing the extension too, is that you can't reply to an email and have your email encrypted. You'll need to compose a new SecureGmail message, which means email threads or conversations isn't supported yet. It's worth noting that only the message body is encrypted, so any attachments you send will need to be encrypted separately.
Otherwise, this is an easy way to send and receive secure messages through Gmail--easy enough for even tech newbies to use.