National Mental Health Association        Many resources from anxiety disorders to healthcare reform. 

Web MD       Tons of information (though can be annoyingly general at times) on all types of mental health issues and conditions. 

Depression Central   This site claims to be the Internet's central clearing house for information on all types of depressive disorders.

Internet Mental Health   Has an online diagnosis feature in addition to a complete directory of disorders, diagnosis, research, and tons more.

Mental Health InfoSource  Home of the Psychiatric Times

National Alliance for the Mentally Ill    News, facts and information about mental illness, updates, links, and help. A very rich resource.

National Institute of Mental Health     Research, science news, updates, and an online anxiety disorder test you can take.

On-Line Psych From ADHD to women's issues. Remarkably thorough.

Psytests.Com     Lot of questionaires you can fill out online and score. Personality, depression and emotional states, I.Q. tests and more