Thunderbird Email Client
Enigmail OpenPGP encryption
Enigmail adds OpenPGP message encryption and authentication to your email client. It features automatic encryption, decryption and integrated key management functionality. Enigmail is based on GnuPG for the cryptographic functions. GnuPG is not part of the installation, but will be downloaded as part of the setup process.
Lightning Calendar for Thunderbird
Lightning allows you to organize your schedule, access remote calendars and much more.
Pretty Good Privacy for Windows for file and email encryption. Gpg4win (GNU Privacy Guard for Windows) is Free Software and can be installed with just a few mouse clicks.
GPGtools MAC Pretty Good Privacy
Use GPG Suite to encrypt, decrypt, sign and verify files or messages. Manage your GPG Keychain with a few simple clicks and experience the full power of GPG easier than ever before.