Web site for Autism Speaks and Cure Autism Now, which says it is the world's largest autism advocacy organization. Concerned with both the medical and scientific aspects of autism as well as raising awareness and helping children and families cope.
Web site of the "TEACCH" program at the University of North Carolina. The program provides a wide range of services for people with autism and their families.
Web site for the Autism Society of America; also the home of Autism Source, an online resource center.
Web site of the Autism Research Institute. According to the site: "ARI is primarily devoted to conducting research, and to disseminating the results of research, on the triggers of autism and on methods of diagnosing and treating autism."
From the National Institute of Neurological Disorders and Stroke: A one page summary plus lots of resource links and access to scientific news, research literature and clinical trials.
From the U.S. National Library of Medicine and the National Institutes of Health, a page rich with links to autism resources of all kinds.
From the National Institute of Mental Health -- more technical than other sites, but worth slogging through for information on current research.
The Centers for Disease Control Autism Information Web site, with links to research, organizations and government information.
How do you explain autism to other children? This site has an informative section about the causes and the treatments.