International Association for Identification
International Crime Scene Investigators Association
Law Enforcement Video Association
International Homicide Investigators Association
International Association of Arson Investigators
National Association of Medical Examiners
International Association of Forensic Nurses
American Board of Medico-Legal Death Investigators
International Association of Blood Pattern Analysts
International Association of Chiefs of Police
Association For Crime Scene Reconstruction
Evidence Photographers International Council
Colorado Coroner's Association

In addition to the national and international associations mentioned above, many with local and regional chapters, there are a multitude of regional organizations focusing on armed robbery, gang-related activities and so forth.

Most of these organizations offer classes and seminars related to their particular area of interest.  The Evidence Photographer's International Council and the International Association for Identification offer widely recognized certification programs.

The International Crime Scene Investigators Association, icsia.org, offers both a certification program and a members forum. Stumped by a problem.  Post the question on the ICAIA member's forum and you will very likely get an answer in short order.