Getting Started in Network Security?

pixelgeek asks: "Security has not only become an important topic but also a critical issue for admins and even the average user in their home. To someone new to the topic the wealth of material can be a bit daunting and, you can imagine, a little confusing. Does anyone have any suggestions on where to start getting a handle on the concept of network/computer security and what are the most important and useful applications (CLI primarily) that a person should examine and learn?" We've touched on these issues before, but it was a while ago. Taking a network security class, could help, but which classes are really worth the money and might there be enough information on the web to make such a choice, unnecessary?