If you're interested in easy-to-use encryption that would protect communications, take a gander at my article this week in TidBITS on public key encryption. This method of encryption allows two or more parties to scramble data in such a way that only a recipient with an appropriate key can decipher it. With more familiar encryption (symmetric key), the same key is used to encrypt and decrypt a file or message. With public key encryption, a pair of keys are used: one public, one private. The public key encrypts; the private decrypts.
Public key cryptography is a broad term, and is used as an element of PGP, a software package that manages people's public keys and uses both public key cryptography and symmetric key cryptography for optimum results.
It's also part of Zfone, which uses what's called a Diffie-Hellman key exchange to provide private calls between two voice over Internet protocol (VoIP) clients. It doesn't work with Skype, but it does with many other packages.