GNU Privacy Guard

GNU Privacy Guard is a free public key cryptosystem suitable for encrypting email and saving encrypted documents. I initially wrote this guide and demo application for a presentation I did in a Cryptography class in college:

A Practical Introduction to GNU Privacy Guard in Windows – walks you through installing GPG on a Windows computer and teaches you how to use the most common functions.
GPG Usage Demo Application – demonstrates how you might call GPG from a Microsoft Access database application before sending data to a remote server.