Here are a few important websites that provide psychology-related information:

General Professional Groups

American Psychological Association (APA)

American Psychological Association of Graduate Students

American Psychological Society (APS)

American Psychological Society Student Caucus

Midwestern Psychological Association (MPA)

Psychology Degree Guide

Clinical Psychology

Association for Behavioral and Cognitive Therapies (ABCT)

International Society for Traumatic Stress Studies (ISTSS)

Society for Behavioral Medicine (SBM)

American Psychosomatic Society (APS)

Association for Death Education and Counseling (ADEC)

Neuroscience, Behavior and Cognition

Cognitive Neuroscience Society

Society for Neuroscience

Industrial/Organizational Psychology

Society for Industrial-Organizational Psychology

St. Louis area I/O group -- Gateway I/O Psychologists

Society of Experimental Social Psychology

Society for Personality and Social Psychology (SPSP)