Encipher.it - Encrypting email with Encipher.it is a simple way to protect your sensitive data.
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
Tutanota - Get your encrypted mailbox for free.
Temp.PM - Temp.PM - Temporary Private Message
Mailvelope - Mailvelope open source project. OpenPGP in your browser.
secserv.me - Create client-side encrypted message. Chat anonymously client-side encrypted.