Off-The-Record Messaging Protocol is a custom tailored encryption scheme for instant messaging based on public key encryption. In addition to the standard benefits of Public Key encryption, such as proving your identity, and encrypting your communication, OTR also offers plausible deniability.

The best part of OTR Messaging Protocol is that its not just a white paper: It has support for most open IM clients. This is the standard for Instant Messaging encryption.

TrueCrypt offers free full-disk encryption for Windows XP, Vista, Mac OS X, and Linux. It lets you choose from multiple encryption algorithms. It provides multiple levels of protection; not only does it encrypt your data, but it even makes it look like no data is there at all to those without the proper access.

They have a “Beginner’s Tutorial’ available. And, its free.

http://www.truecrypt.org/