American Association of Physicists in Medicine (AAPM)
http://www.aapm.org/  

American College of Radiology (ACR) 
http://www.acr.org/  

American Nuclear Society (ANS)
http://www.ans.org/  

American Physical Society (APS)
http://www.aps.org/  

American Roentgen Ray Society (ARRS)
http://www.arrs.org/ 

American Society for Emergency Radiology
http://www.erad.org/ 

American Society for Therapeutic Radiology and Oncology (ASTRO)
http://www.astro.org/ 

American Society of Radiologic Technologists (ASRT)
http://www.rsna.org/about/  

Code of Federal Regulations and Federal Register Online
http://www.gpoaccess.gov/fr/index.html  

Conference of Radiation Control Program Directors (CRCPD)
http://www.crcpd.org  

Council on Ionizing Radiation Measurements and Standards (CIRMS)
http://www.cirms.org/  

Health Physics Journal
http://www.health-physics.com  

Health Physics Society
http://www.hps.org/  

Institute of Electrical and Electronics Engineers (IEEE)
http://www.ieee.org  

International Atomic Energy Agency
http://www.iaea.org/  

International Nuclear Energy Research Initiative
http://www.pnl.gov/ineri/  

International Organization for Medical Physics
http://www.iomp.org/  

International Radiation Protection Association
http://www.irpa.net/

National Academy of Sciences
http://nationalacademies.org/ 

National Council on Radiation Protection and Measurements (NCRP)
http://www.ncrp.com/

National Institute of Standards and Technology (NIST)
http://www.nist.gov/  

NIST Ionizing Radiation Lab
http://physics.nist.gov/overview/div846bro.html  

National Institutes of Health (NIH)
http://www.nih.gov/  

National Laboratories (US DOE)
http://apollo.osti.gov/html/servers/labtitls.html  

National Nuclear Data Center
http://www.nndc.bnl.gov/  

National Radiological Protection Board
http://www.hpa.org.uk/radiation/

National Science Foundation
http://www.nsf.gov/  

U.S. Nuclear Regulatory Commission
http://www.nrc.gov/

NRC Reference Library
http://www.nrc.gov/reading-rm.html  

Nuclear Energy Institute (NEI)
http://www.nei.org/  

Nuclear Energy Research Initiative
http://neri.ne.doe.gov/  

Particle Physics and Data
http://pdg.lbl.gov/pdg.html  

Physical Reference Data NIST  
http://physics.nist.gov/PhysRefData/contents.html  

Physikalisch-Technische Bundesanstalt Ionising Radiation
http://www.ptb.de/en/org/6/_index.htm   

Radiation Effects Research Foundation
http://www.rerf.or.jp  

Radiation Safety Information Computational Center ORNL
http://www-rsicc.ornl.gov/  

The European Synchrotron Radiation Facility
http://www.esrf.fr/

The Radiological Society of North America
http://www.rsna.org/  

The Society of Nuclear Medicine
http://www.snm.org/  

University of Michigan Health Physics
http://www.umich.edu/~radinfo/

World Collection of Radiation Links
http://www.eneabba.net/radlinks/index.html

Occupational Safety and Health Administration
http://www.osha.gov/SLTC/radiation/

Publishers, Books and Journals
http://www.umich.edu/~radinfo/professional/commercial/publish.htm

Radiation Safety Offices
http://www.umich.edu/~radinfo/professional/radsafe.htm  

Radiological and Radiation Modeling
http://www.umich.edu/~radinfo/professional/model.htm  

Regulations Codes Orders Standards and Laws
http://www.umich.edu/~radinfo/professional/law.htm  

Software
http://www.umich.edu/~radinfo/professional/software.htm  

State Regulators and Information
http://www.umich.edu/~radinfo/professional/states.htm  

U.S. Federal Regulators and Information
http://www.umich.edu/~radinfo/professional/feds.htm