GPGMail - GPGMail is an open source plugin for Apple Mail.
Encrypto - Encrypto lets you encrypt files before sending them to friends or coworkers.
ProtonMail - Secure email with absolutely no compromises. Get your free encrypted email account today.
VeraCrypt - VeraCrypt is a free open source disk encryption software for Windows, Mac OSX and Linux.
Enigmail - Security extension to Mozilla Thunderbird and SeaMonkey
TrueCrypt - TrueCrypt is a leading cross-platform that provides encryption tools that allow you to migrate any encrypted data to virtual disks images on your systems.