OpenPGP is a standard (rfc 4880) for providing secure information storage and transmission using a cryptographic system such as Symantec's PGP or the free GPG (GNU Privacy Guard) software. Uses include such things as encrypting files, whole disks encryption, encrypted emails, creation of digital signatures, etc.
Symantec has a full range of PGP software depending on what one requires. Endpoint software for whole disks and removable storage; Email solutions; File level protection using PGP commandline; Application and Key Management software. These are generally available for Windows, Mac and Linux platforms.
GnuPG provides free commandline OpenPGP compatible tools. Graphical front-ends are available, as well as plugins to common Email clients. Available for Microsoft Windows, Mac OS X, Linux, *BSD, etc.
Most distributions have packages available to easily install GPG, or are already installed if using KDE or GNOME desktop environments. Refer to your Operating System's documentation for infromation on installing packages.
Some general examples will be available on the Information Security Best Practice Toolkit