RFC 2015 defines a proposed Internet standard for sending PGP-encrypted email. This PGP/MIME has been incorporated into several MUAs such as Mutt and (with the AEGYPTEN project) KMail. However, a lot of email clients still don't support it. pgp-mime-handler can decrypt/verify such messages via a pipe, so it can be used as an email filter in many programs or scripts.
Gale is an open-source messaging system. It provides private messaging and public chat, uses strong end-to-end cryptography for security, and supports a distributed server network with a range of clients (both console and GUI) available. Gale is currently in early alpha testing. See the homepage for the details of its current status.
KCrypto is a KDE2 file encryptor. It uses the Rijndael public domain C++ class implementation, and is capable of encrypting and decrypting every kind of file (text and binary) in CBC mode with a 32-byte key (256 bits) very quickly. Its purpose is to provide a more secure alternative to passworded .zip files or giving the user the chance to store or send a file via the Internet in reasonable security.
LockBox is a tool for the Palm Pilot and compatibles that helps users securely manage account information. Multiple account information is protected by a single password. Features: Stores Account Information - Account Name, User Name, Password, Notes, Export data to Memo Application, Categories to organize different account information, 128bit (A)RC4 Encryption, Works on PalmOS2.0 and higher devices, Backs up changes to PC during HotSync.
Keyring for PalmOS lets you securely store secret keys and confidential information on a PalmOS handheld computer. This information might include computer account passwords, credit card numbers, GnuPG or PGP passphrases, SKey one-time-pads, or phone banking keywords. Records are encrypted using the well-trusted DES3 algorithm on a master password. When you need to set a password, Keyring can generate a random password of specified length, optionally including letters, numbers, or symbols.
ftp-ssl is similar to the standard FTP client and it interoperates with normal ftpd, but it uses SSL authentication and encryption. It checks if the other side is also talking SSL, and if not it falls back to the normal FTP protocol. Advantages over normal FTP include encryption of passwords and transmitted data, preventing network sniffers from acquiring secret information (most notably passwords).
linux-ftdp-ssl is the netkit ftp server with encryption support. ftpd-ssl replaces normal ftpd using SSL authentication and encryption. It operates together with normal ftp. It checks if the other side is also talking SSL, if not it falls back to normal ftp protocol. Advantages over normal ftp(d) are that your passwords and the data you send will not go in cleartext over the line, and nobody can get it with tcpdump or similar tools.