IT Security Tutorial Websites
Basic and advanced security topics by About.com. The site also provide topics on web security, email security and others.
E-mail and spam security from About.com. The site has lots of useful tutorials and information in in other security areas as well.
IPSec architecture by Microsoft Technet.
managed communications is a VPN service provider and note some basic key differences of VPN services for businesses with simple diagrams.
OpenVPN provide a tutorial on how to setup and use their open source SSL product.
Setting up VPN in a Microsoft environment by Microsoft Technet.
SSL VPN in depth guide with lots of useful information.
VPN technologies are provided in this article and an overview of the differences by Tech Republic.