Tor ("The Onion Router") has been up and running for some time. It's a free and highly secure system for anonymous browsing. It requires installation of free, open source software on the host machine.
Also of potential interest is the current release of Freenet, which supports a "scalable darknet:"
A freeware, open source distribution of PGP (named, appropriately, GPG).
A GPG for Windows front end.
TrueCrypt (a freeware/open source hard drive encryption/steganography program)
The Electronic Privacy Information Center (EPIC) tools page
Hushmail: secure, free web mail
Secure, free hard drive/file erasure
Disclaimer and warning: Strong cryptography isn't legal everywhere. The United States, for example, still regards some types of cryptographic algorithms as munitions, and export is forbidden. Know your country's laws before you proceed. Cryptography isn't a panacea for our loss of privacy in the digital age. It is, however, a very powerful tool to put an envelope back on your mail, a lock on your computer's "filing cabinet," to destroy sensitive files or to send a letter without a return address - all things our parents took for granted. Learn its limits and use it wisely for your own sake and everyone else's. Do not attempt to send threats, traffic in drugs or child pornography, plan acts of terrorism or engage in other crimes using crypto. Sooner or later, you'll draw attention to yourself and the full weight of the law will come down, hard. You will be caught, you will be prosecuted, you will be imprisoned. Period. Regards, - Moriarty