Nerk

RigFlex is a Blender add-on that brings simple soft body simulation to armatures. It applies soft body actions to parts of a rig using a stable, first order simulation, with baking once the animation is finished.

FishSim is a Blender add-on by Nerk that simulates the swimming action of a fish chasing a target. It ships with three pre-rigged fish models: a Shark, a Goldfish, and an Archer Fish.

Add Airfoil is a Blender add-on from Nerk that imports airfoil dat files into your scene. It supports the Selig format and adds an entry to the File/Import menu for bringing profiles in as mesh.