The US National Institute of Standards and Technology (NIST) has a nice series of IT guides many of which are focused on security. They are rarely short documents but well worth the time for managers and administrators. To give you an idea of the range they cover here are few that I have found useful:
- Guidelines for Securing Wireless Local Area Networks (WLANs)
- Guide for Security-Focused Configuration Management of Information Systems
- Guide to General Server Security
- Guide to Intrusion Detection and Prevention Systems (IDPS)
- Guide to Computer Security Log Management
- Guide for Applying the Risk Management Framework to Federal Information Systems: A Security Life Cycle Approach
There are many, many more. These are excellent and free resources. I found them useful guides for the development of IT management plans and as introductions to specific IT problems such as log management.