Solid advice on securing your home Wi-Fi network: This straightforward About.com article notes six steps to securing your network, all of which are sensible and well explained. (The link is for page 2; page 1 explains what Wi-Fi is.)
Along these lines, Windows XP users should note that Microsoft recently released a set of patches that fix 802.1X and WPA problems. Read the summary. Point No. 6 in the About.com article is to keep current on patches!