MySQL Workbench is a cross-platform, graphical database modeling tool for MySQL. It allows you to create database models from scratch as well as by importing existing databases from SQL or DBDesigner4 models. You can then generate SQL code to CREATE databases, ALTER them, and export in various image formats and PDF/PS. Its extension system allows writing plugins and scripts in Lua, Python, and C++.
Open DESIRE is a modeling/simulation language for dynamic systems and neural networks, a runtime compiler, and an experiment-protocol script for simulation studies. It supports up to 40,000 differential equations or neural networks, in scalar and/or vector form. It also supports very fast Monte Carlo studies and complex frequency-response plots.