Copyright (c) (copr) 1997 all rights reserved by TJH Internet SP and Earth Operations Central. All comments are strictly my unsupported opinion unless based upon promotional blurb extracted from the websites linked herein. This is by no means an exhaustive nor definitive list, and no particular recommendation nor assurance of solvency or utility is to be inferred from a listing herein.
Computational Modelling & Simulation

See also:

As computers become more powerful, mathematical models can be developed which ever more closely conform to reality. These models can be used to develop simulations, which can be used to predict emerging realities, and may also be used to develop methodologies for shaping emerging realities.

For a fun simulation site, see Technosphere, which simulates an alien ecology.