The two you listed are definitely the main ones for bipeds and quadrupeds (quadruped rigs generally have an extra joint in back leg's ik chain, obviously). I've also used IK handles in an eye rig -- I put one joint in the center of the eye, and one joint out in front of the character, where I want the controller to be. Then, I create an IK handle between the first joint and the second one, and bind the eye to the first joint. The IK handle is parented to the controller. Often the back and neck use an IK Spline, which uses a curve to control the rotations of joints in a chain.
In general, IK is used when the rigger wants to manipulate a joint hierarchy from the end of the hierarchy. That's why it's so useful for limbs -- you can put a hand (end joint) somewhere, and the elbow and shoulder (i.e. joints higher up the joint chain) rotate automatically to accommodate the end joint's position.
