I really like the idea of the Take Control series of instructional PDF documents. For $5, I purchased the Take Control of Your AirPort Network book (155 pages!), by Glenn Fleishman, and used it to improve the setup of my home WiFi network. Now, I have my Airport Extreme base station secured with the WPA Personal authentication and encryption system, have configured my network with an Access Control List, and have my Airport Express setup as a WDS bridging network extender, with AirTunes music streaming enabled.
Figuring out how all this stuff works together and making sensible decisions (Which encryption? Does WDS work with music streaming?, etc.) can be done through a combination of reading Apple’s documentation, Googling, and reading through some of the Wifi forums, but finding all this in one convenient electronic document is to me well worth the $5.