Dumbill, Edd, Brian Jepson, and Roger Weeks. Linux Unwired. Sebastopol, CA: O'Reilly & Associates, 2004. This book includes one of the more concise and clear explanations of WPA I've seen, plus detailed instructions on creating end-to-end-Linux WPA solutions.

Gast, Matthew. “A Technical Comparison of TTLS and PEAP.” www.oreillynet.com/pub/a/wireless/2002/10/17/peap.html?page=last&x-maxdepth=0 . This on-line article spells out the most important differences among EAP-TLS, PEAP and EAP-TTLS.

Malinen, Jouni. hostap.epitest.fi. Home page for wpa_supplicant, a WPA supplicant for Linux; hostap, a driver for Linux-based APs using Prism WLAN hardware; and hostapd, a WPA-enabled access point daemon package. Besides this essential software, Jouni also provides much useful documentation.

Strand, Lars. “802.1X Port-Based Authentication HOWTO.” www.tldp.org/HOWTO/html_single/8021X-HOWTO. A concise but narrow-scoped guide to setting up WPA with Xsupplicant, Cisco WLAN access points and FreeRADIUS to use 802.1x authentication. As of this writing, Xsupplicant supports only 802.1x authentication, not TKIP encryption.

www.freeradius.org is the home page for the FreeRADIUS project, where you can download the latest FreeRADIUS software and documentation.