WPA

I picked up this from BoingBoing - Glenn Fleishman and Adam Engst made a book about how to set up and maintain a secure Wireless LAN in 2004. Today, they have decided to give the book away for free.

The download is at their website.

Please note that the book does not cover WPA and other new security measures. It is, however, a great general resource to plan and execute your WLAN.