GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
GPG4Win - GPG4Win is an encryption program for files and emails. The program encrypts emails and files so that they can only be read by those intended to receive them.
S.S.E. File Encryptor - S.S.E. File Encryptor is a cross-platform encrypter/decrypter of files and folders.
Autocrypt - Convenient End-to-End Encryption for E-Mail
Chatlink.com - Anonymous communication platform
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.