Open Source Simulators
2D Simulators
Commercial Simulators
Havoc(3D, free for non-commercial and inexpensive commercial PC games, fee-based for games above a price limit, non-game applications, and consoles.) Try Havok.
SPE Simple Physics Engine (3D, free for noncommercial, fee-based for commercial)
Chrono::Engine (3D, free for noncommercial use, fee-based for commercial)