Various Simulation Sites:
Centre for Medical Simulation
Debrief2Learn
Foundation for Healthcare Simulation Safety
Healthcare Simulation Middle East (NEW!)
Healthy Simulation
ImPACTS (Improving Pediatric Acute Care Through Simulation) (NEW!)
Innovative SimSolutions
INSPIRE (The International Network for Simulation-based Pediatric Innovation, Research, & Education) (NEW!) 
Simulating Healthcare
True Plastic Surgery

Moulage:
Please see the Moulage section for relevant links

Scenario / Visual Stimuli Databases:
SimBox + Tele SimBox (Simulation Cases + Step-by-step guide on facilitating a simulation) (NEW!)
ALiEM - Academic Life in Emergency Medicine (Simulation Cases + EM Sim Curriculum for Pediatrics) (NEW!)
BC Simulation Network Simulation Scenario Repository
EM Sim Cases
Internal Medicine Simulation
Radiopaedia
Simulation Canada - SIM Scenario Exchange
The Simbook

Organizations:
Association for Simulated Practice in Healthcare (ASPiH)
Association of Standardized Patient Educators (ASPE)
The Canadian Alliance of Nurse Educators using Simulation (CAN-SIM)
Dutch Society for Simulation in Healthcare (DSSH)
International Nursing Association for Clinical Simulation & Learning (INACSL)
International Pediatric Simulation Society (IPSS)
Israel Center for Medical Simulation (MSR)
Sociedad Española de Simulación Clínica y Seguridad del Paciente (SESSEP)
SimGhosts
simLEARN
Simulation Australasia
Simulation Canada
Society for Simulation in Healthcare (SSH)
Society in Europe for Simulation Applied to Medicine (SESAM)

Vendors:
3-Dmed
7S3 (7 Sigma Simulation Systems)
Avkin
CAE Healthcare
Cardionics
Echo Healthcare
Education Management Solutions (SIMULATIONiQ)
Engenium Staffing/Recruiters
Gaumard
IngMar Medical
Inovus Medical
iSimulate
KbPort
KwickScreen
Kyoto Kagaku
Laerdal Medical
Lecat's Ventriloscope
Level 3 Healthcare
Lifecast Body Simulation
LifeLike BioTissue
Limbs & Things
MedicFX
MedVision
Michigan Instruments
Mimic Simulation
MODEL-med International
Nasco
Neosim AG
Nordic Simulators
Operative Experience
OtoSim
Pocket Nurse
Realists Surgical Spine
Remedy Simulation Group
Sawbones
Simbionix
SimScreen
Simskin
SIMStation
Simulab
Simulare Medical
Simulation Collective
Sim U Suit
SonoSim
Surgical Science
Symgery
Synaptive
SynDaver
The Apprentice Doctor
The Chamberlain Group
Vata
VitalsBridge
VirtaMed
Wallcur

Podcasts:
Centre for Medical Simulation - DJ Simulationistas
Simulcast

Apps / VR / AR:
Acadicus (VR)
Awesome Ultrasound Simulator App
DART Sim (ECG)
Fundamental Surgery (VR)
Insimo
MedCognition (AR)
Med Sim Studio (Vital Sign software)
OSF Healthcare (AR)
OSSO VR (VR)
Oxford Medical Simulation (OMS) (VR)
Precision OS (VR)
Proven Reality (AR/VR)
Sim X (VR)
SimMon (Vital sign App)
TruMonitor (Vital Sign App)
UbiSim (VR)

Know a useful simulation website not listed?
Let me know.