Enigmail is an extension to the mail client of Mozilla Thunderbird / Seamonkey, Netscape which allows users to access the authentication and encryption features provided by GnuPG.

The GPGServices service plugin adds to the global Services menu (in the Application menu) the facility to sign and verify plain text in any application that supports text services. The plugin also provides convenience facilities to import an ascii-armoured key from text in any application as well as return your default key, in ascii armoured format, and the key's fingerprint.

Note: GPG tools [http://www.tomsci.com/gpgtools] is a closed source equivalent to this project, even if the author is prepared to provide the source code there will always be a trust question regarding the distribution binary.

Although Apple's Address Book provides central management of your contacts' details, it was previously necessary to use different applications to manage their GPG keys. The ABKey plugin enhances Address Book by allowing you to see which of your contacts have current, revoked and expired keys as well as providing more detailed information on request.

GPGMail is a plug-in for Apple's Mail, providing a front-end to gpg for some operations. It allows you to read/write encrypted messages, as well as electronically signed messages.

Applescripts for Eudora X to encrypt, decrypt, sign and verify plain text messages using the MacOS X port of Gnu Privacy Guard (GnuPG).

An open source Mac OS X SFTP, SCP and SSH Frontend from the University of Michigan licensed under a BSD-style license.

Another open source SFTP (SSH Secure File Transfer) and FTP browser licensed under the GPL. Note: Requires OS X 10.3+.