American Masters on PBS features a biography of Serling on the series' web site.
Authors and Artists for Young Adults. Vol. 14. Gale Research, 1995
The Rod Serling Memorial Foundation is dedicated to preserving Serling's contributions to the arts. There are several interviews with Serling on this site, including "Rod Serlings's Final Interview," March 4, 1975, by Linda Brevelle. You'll also find a list of links to other web sites that feature Serling or his work.
The Twilight Zone Site has a collection of links about Rod Serling, everything from his birth certificate to his obituary.
Selected Books about Rod Serling
Engel, Joe, Rod Serling: The Dreams and Nightmares of Life in the Twilight Zone (biography). Chicago: Contemporary Books, 1989.
Sander, George F. Serling: The Rise and Twilight of Television's Last Angry Man. New York: Plume, 1994.