Secure Your Home Wireless Network for Free

From Extremetech.com

Secure Your Home Wireless Network for Free
January 15, 2008 By Joel Durham Jr.

It's startling how easy it can be to swipe data from wireless networks.
I live in a townhouse, so I'm at close quarters with my neighbors. It irks me when, for one reason or another, my Wi-Fi enabled notebook discovers nearby networks lacking any sort of security at all. Were I the nefarious type, I could waltz onto their network and look for shared folders containing sensitive data, leech their Internet connections, steal their media, monitor their network activity, and so on.

Entire article, lots of reading but simple, good information.