Where to Get PGP
As of June 2010, PGP Corp was acquired by Symantec. Now PGP is available only from Symantec.
PGP is now in the hands of its fifth owner. First there was me, then PGP Inc (I was chairman and CTO of that company), then Network Associates, then PGP Corp, and now Symantec.
PGP Freeware and Source Code
Symantec no longer offers a freeware version of PGP. For several years they allowed the public to download the source code for peer review. But now that link seems to no longer have source code available. Perhaps they will again make source code available in the future, if enough paying customers ask them to.
Today, the best place to get source code for a great implementation of the OpenPGP standard is Gnu Privacy Guard (also known as GnuPG or GPG). GnuPG runs on Linux, Windows, and Mac OSX. It is available as a command-line version, or as a GUI version.
If you want a highly mobile way to do PGP-style encrypted email, you might consider HushMail, from Hush Communications. HushMail is a web-based encrypted email service that uses a downloaded Java applet to encrypt and decrypt email in your browser. There's nothing to install, because it's all done in your browser. Which greatly simplifies deployment in large corporate environments. It's also handy for road warriors who might need to check their encrypted email from an Internet cafe. And for all you Macintosh fans, HushMail also works with Safari on Mac OS X. Sign up to try out HushMail for free, but if you pay for an upgraded subscription, you get better service and you will be keeping another OpenPGP vendor in business, which the OpenPGP community really needs.
You can find other providers of OpenPGP-compliant software at openpgp.org, under the "Members" tab.