Agent-based modeling

Packages and IDEs (Integrated Development Environments)

NetLogo - has its own interpreted object-oriented language.
1. Pros: free; platform-independent; probably the easiest IDE for agent-based modeling; easy to make a GUI (Graphical User Interface; e.g. add sliders for variables, add plots, and so on), lots of built-in functionality, including built-in loops ("forever" checkbox on the Go button as well as the "ask" keyword). Quick learning curve.
2. Cons: run-time can be a bit slow for some things; has its own syntax; might be difficult to implement new functionality. Error messages can be a bit misleading.
Repast - a library package for agent-based modeling designed to work with Java (platform-independent) or C# (Microsoft Windows only).
MASON - Multi Agent Simulator Of Networks and Neighborhoods from George Mason University. MASON consists of a library of Java objects for constructing, instrumenting, and visualizing ABMs.