polymake is a tool to study the combinatorics and the geometry of convex polytopes and polyhedra. It is also capable of dealing with simplicial complexes, matroids, polyhedral fans, graphs, tropical objects, and other objects.
In the Wiki you can find the growing collection of documentation related to the mathematical software package polymake, as well as extra material supplied by the user community. There you can download the software and find the extensions.
More information about the polymake software can be found on its homepage.