OMNeT++ is an extensible, modular, component-based C++ simulation library and framework, primarily for building network simulators.
GLAST (Gamma Ray Large Area Space Telescope) project
Curt Brune's page reports about using OMNeT++ for the GLAST (Gamma Ray Large Area Space Telescope) project (see also "LAT Event Simulation" document below). The page shows examples of using the ROOT graphing package to visualize simulation results. ROOT has impressive visualization capabilities, and it is relatively easy to integrate with OMNeT++. Home page: http://www.slac.stanford.edu/~curt/omnet++
Bertrand Hechenleitner and Karl Entacher have performed different simulations to examine bad effects of poor RNGs on simulation results. They suggest two RNGs to be used: Mersenne Twister and the Objected-Oriented Random-Number Package of Pierre L'Ecuyer et al. Source available from the page. Home page: http://www3.fh-sbg.ac.at/~bhechenl/research.htm