Healthcare professionals join together to meet many professional needs. Here is a basic list that will introduce you to both the industry itself, and organizations dedicated to information technology.

American Health Information Management Association (AHIMA)
American Association of Integrated Healthcare Delivery Systems (AAIHDS)
American Hospital Association (AHA)
American Medical Association (AMA)
American Medical Informatics Association (AMIA)
American Telemedicine Association  (ATA)
Canada Health Infoway - Extensive array of resources
Canadian Healthcare Information Technology Trade Association
California Healthcare Foundation (CHCF)
College of Healthcare Informatics Executives (CHIME)
Computer-Based Patient Record Institute (CPRI)
Community Health Information Technology Alliance (CHITA)
COACH, Canada's Health Informatics Association
eHealth Initiative (eHI)
Healthcare eBusiness Collaborative (HEDIC)
Healthcare Information and Systems Management Society (HIMSS)
Institute of Medicine (IOM)
Joint Commission on Acreditation of Healthcare Organizations (JCAHO)
Managed Care Information Center   (MCIC)
Medical Records Institute  (MRI)
Microsoft Healthcare Users Group   (MSHUG)
National Managed Healthcare Congress (NMHCC)
Radiological Society of North American  (RSNA)
RHIOWiki – Brand new RHIO site, a first with comprehensive information