• Office of Laboratory Animal Welfare (OLAW): NIH
• Association for Assessment and Accreditation of Laboratory Animal Care International (AAALAC)
• The Animal Welfare Information Center: USDA
• American Association for Laboratory Animal Science (AALAS)
• IACUC Central (a comprehensive resource from AALAS)
• Institute for Laboratory Animal Research (ILAR)

Books / Guidelines (free download)

• The Guide for the Care and Use of Laboratory Animals, 8th Ed. (2011) 
  The National Academies Press
• AVMA Guidelines for the Euthanasia of Animals: 2020 Edition
• Institutional Animal Care and Use Committee Guidebook, ARENA & OLAW, 2nd Ed.
• Occupational Health and Safety in the Care and Use of Research Animals (1997)
  The National Academies Press

Training Site

CITI Program (Collaborative Institutional Training Initiative)