Tool support for creating FMC* diagrams [Block diagrams, Petri nets, Entity-Relationship diagrams (ERD)] in MS-Visio 2000 and newer. Features: stencils, consistency checking, Petri net simulation, exporter e.g. pdf, ... *Fundamental Modeling Concepts
A stripped down version of the stencil set is available for TAM (Technical Architecture Modeling of SAP). This set uses UML notation and contains Block, Activity, Sequence, State, Class, and Component diagrams. It doesn't contain Simulation, exporter, or even shape help.
great app, works nicely