The MotionBoutique in the last little while have released Newton, a complete 2D physics engine environment for After Effects which represents an easy and quick plugin for any type of simulated rigid animation. Newton interprets each 2D layer as a rigid body in a real environment. Once simulation is completed, animation is recreated in After Effects with standard keyframes.
If you are curious as to how Newton is integrated and what the workflow is like in After Effects, the MotionBoutique have posted an in-depth look at some simple simulated physical interactions and what the workflow is with layers and assets coming from Illustrator or Photoshop.
