Professional:
Association of Firearm and Tool Mark Examiners
American Academy of Forensic Sciences The AAFS is the largest professional organization for forensic scientists in the U.S.
American Society of Crime Laboratory Directors Offers guidelines for forensic laboratory management practices, a code of ethics, and information on their voluntary accreditation program for crime laboratories. An employment directory searchable by state, and recent issues of ASCLD NEWS, the society's newsletter, are also available.
California Association of Criminalists
Canadian Society of Forensic Science Society's site includes a history of the CSFS & the Royal Canadian Mounted Police Laboratory System, STR DNA data in Excel spreadsheets, table of contents for the Society's journal (1995 to present) as well as book reviews (1999 - 2002).
Chartered Society of Forensic Scientists (UK) British forensic science professional organization.
Forensic Technology Center of Excellence offers free online training for forensic professionals. From the Research Triangle Institute, funded in part by grants from the NIJ.
IAI – International Association for Identification https://www.theiai.org/
International Association of Forensic Toxicologists.
Internet Pathology Laboratory for Medical Education: Forensic pathology Developed for medical students, shows images, etc. Warning: images are graphic. Includes mini-tutorials on Firearms and Drug Abuse Pathology.
ISFG – International Society for Forensic Genetics http://www.isfg.org/
MAAFS – Mid-Atlantic Association of Forensic Scientists http://www.maafs.org/
MAFS – Mid-Western Association of Forensic Scientists http://www.mafs.net/
National Pesticide Information Center A collaborative project of Oregon State University and the U.S. Environmental Protection Agency.
New York City Office of the Chief Medical Examiner. Including a link to the forensic science training program.
New York City Poison Control Center.
NEAFS – Northeastern Association of Forensic Scientists http://www.neafs.org/
NIJ – National Institute of Justice http://www.nij.gov/Pages/welcome.aspx
NIST Forensics – National Institute of Standards and Technology http://www.nist.gov/forensics/
SAFS – Southern Association of Forensic Scientists http://www.southernforensic.org/
SWAFS – South-Western Association of Forensic Scientists
U.S. Fish and Wildlife Service Forensics Laboratory Dedicated to investigating crimes against wildlife; poaching, smuggling, etc.
WHO: International Programme on Chemical Safety. Through the International Programme on Chemical Safety (IPCS), WHO works to establish the scientific basis for the sound management of chemicals, and to strengthen national capabilities and capacities for chemical safety.
Popular:
Reddit forum for discussions on forensic science topics.
Visible Proofs: Forensic Views of the Body The history of Forensic Medicine, an exhibit at the National Library of Medicine.
Crime Scene Investigation Network Popular website, includes practical articles written by practitioners. Lots of advertising.
Questioned Document Examination Page of Emily Will Theories, applications, and famous cases in questioned document examination from , a certified document examiner.
Zeno's Forensic Site A classic list of resources, unfortunately no longer kept up to date.