National:

U.S. Department of Health and Human Services Substance Abuse and Mental Health Services Administration (SAMHSA)
http://www.samhsa.gov/  

National Alliance for the Mentally Ill
http://www.nami.org/

Mental Health America
http://www.nmha.org/

Depression and Bipolar Support Alliance
http://www.dbsalliance.org/

Local Support/Advocacy Groups:

National Alliance for the Mentally Ill-Jacksonville
http://jacksonville.nami.org/  
  
Consumer Support Services, Inc.
http://www.cssinc.org/
   
Mental Health America of Northeast Florida
http://www.mhajax.org/

Depression and Bipolar Support Alliance
http://www.dbsajacksonville.org

Mental Health/Substance Abuse Treatment Providers:

River Region Human Services
http://www.rrhs.org/

Gateway Community Services
http://www.gatewaycommunity.com/

Northwest Behavioral Health Services
http://www.iwebcenters.com/nbhs2002

Ten Broeck Hospital
http://www.tenbroeckjax.com/

Community Rehabilitation Center
http://www.crcjax.org/

Local Information and Referral/Crisis Line: 

United Way-211 (also known as First Call)
http://www.nefl211.org/