GfA Aerophysics Simulation Services
Wind Engineering, Ventilation and Air Quality Consulting, Ingenieurdienstleistungen rund um Luft, Wind und Bauwerke
http://www.gfa.de/

Berkeley National Laboratory (LBNL) Simulation Research Group
Building Energy Simulation Programs: DOE-2, EnergyPlus, and SPARK.
http://gundog.lbl.gov/

Paragon Simulation
Software for industrial engineering, production simulation and process optimisation. Specialise in building generic, enterprise-wide models of industrial processes.
http://www.paragonsimulation.com

Environmental Simulation Center
The Environmental Simulation Center is an independent, not-for-profit planning and urban design firm, specializing in applying information technology and decision support systems in real-world planning, design, development, and environmental and visual impact projects.
http://www.simcenter.org/

HailCalc - Hail Damage Simulation
HailCalc provides an online hail storm simulation environment, where insurance companies can calculate building/car damage due to real hail storms moved/rotated over particular locations. Uses leading research from ETH Zurich.
http://www.hailcalc.com

ACIMS -- Arizona Center of Integrated Modeling & Simulation
Artificial Intelligence and Simulation Group. The page contains summaries of ACIMS simulation projects, simulation links, and news. One of the main research projects is the Discrete Event Specification Formalism (DEVS).
http://www.acims.arizona.edu/

Averill M. Law and Associates
Averill M. Law & Associates offers simulation consulting, simulation training, and the ExpertFit distribution-fitting software. It was founded in 1977.
http://www.averill-law.com/

Tau Simulation
Tau Simulation produces high performance simulation software for integrated circuit verification
http://www.tausim.com/

CADwalk
Process simulation, device simulation, and circuit simulation as services. Specialties include working with SiGe HEMT, HBT, and MOSFET.
http://www.cadwalk.de/

C++SIM
_your description goes here_
http://cxxsim.ncl.ac.uk/