There are many professional organizations for psychologists and psychology students.  Many of these sites have information that might be valuable to you, whether you are (or become) a member or not. 

National Professional Associations

American Psychoanalytic Association
The professional organization of psychoanalysts — mental health providers (usually M.D.s) who use the theories and therapy methods originally developed by Sigmund Freud. 

American Psychiatric Association
The professional organization of M.D.s who specialize in the diagnosis and treatment of mental disorders.  This is the APA that publishes the Diagnostic and Statistical Manual of Mental Disorders. 

American Psychological Association
The world's largest organization of psychologists. 

American Psychological Society
The professional organization of primarily academic psychologists throughout the United States.  Many teaching resources, and much more. 

Association of Black Psychologists

Australian Psychological Society

Canadian Psychological Association

National Mental Health Association

Academy of Counseling Psychology
American Academy of Child and Adolescent Psychiatry
Association for Academic Psychiatry
European Society for Developmental Psychology
PSI BETA - The National Organization's Page
PsiBeta is the national honor society for psychology students at two-year colleges. 
     Psi Beta - Massachusetts Bay Community College
     Psi Beta - Mineral Area College
     Psi Beta - Tulsa Community College
Psi Chi
Psi Chi is the national honor society for psychology students at four-year colleges and universities. 
Society of Behavioral Medicine
Society for Computers in Psychology (SCiP)
Society for Consumer Psychology
Society for Gestalt Theory and its Applications (GTA)
Web Psychological Club

Iowa Psychological Association
Oklahoma Psychological Association
Oklahoma Psychological Society

Discussion Groups
A number of discussion groups, both for psychology faculty and for students have been established.  Each is devoted to different interests, so check the descriptions.  Addresses of Note contains information about hundreds of discussion groups that deal with topics of interest to psychologists and psychology students.  Though out-of-date, most of the information appears to be accurate. 

News and Announcements
Danilo Curci has set up Psych News and Announcements Digest, a forum for posting news and announcements about psych events. 

Other Links to Organizations, Societies, Acadamies, etc.
Psychnet-UK has as complete a list of professional groups as you are likely to find anywhere.