GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
Chatlink.com - Anonymous communication platform
Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
Autocrypt - Convenient End-to-End Encryption for E-Mail
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.
CrococryptFile - Strong file encryption tool