http://www.subspacef...ty_concepts.pdf <-free PDF eBook
Nice little book which is basically a set of dot points about a wide range of security concepts, all relating to IT in some way. It even has a chapter on Forensics.
There are a lot of references/external links, so the book isn't cluttered. But like anything if you take interest in something noted in the book ... well you're using the internet, so go wild
Almost every security concept is covered (from what I've read so-far), they're all important to include in an IT/Information/Data Security Plan, if you ever find yourself writing/compiling one.