I wrote a series of online security presentations using Google Docs a while back for end users, and thought other members of DP might benefit. They cover everything from basic computer security, digital certificates, social engineering, multi-factor authentication, encryption, captchas, DNS, XSS, SQL injections... They are listed based on skill level from Beginner to Advanced. http://www.securitypresentations.com/ Feel free to leave feedback on the site or here.