Blender 2.66: Rigid Body Simulation
The Bullet physics library has now been integrated into the editor and animation system, which makes rigid body simulations available also outside of the game engine. This results in a much simpler workflow and gives more control over the simulation.
Objects can be added to the rigid body world and become dynamic.
The rigid body simulation supports Blender's force fields.
Rigid Body Constraints
Constraints can be used to connect rigid bodies and build complicated dynamic structures. They're breakable and can be used to simulate destruction.
Next to the ability of baking the simulation to keyframes, rigid bodies can also use the point cache system for a faster workflow and better playback performance.