This person has some great ideas on how to use constraints to keep an object to a path, rig a piston, rig a jet exhaust, He uses the snap to curser shift s keyboard shortcut. He has some parts which don't constrain properly, and he shows you how to fix those issues.
He has good examples, and how to set up constraints in those. He talks about copy scale constraint, and rigging some shutters for a window. He goes over how to use the limit distance constraint and Limit Location and limit scale with good examples. Also the transformation constrainte with a wheel on a landscape.
He uses constraints to rig a robot arm.
He makes a landing gear type object, and also selects an object, goes to edit mode, select a piece and then shift s to make the selection to object (center) So he can attach the bone in the right area (so it rotates correctly). He uses constraints for the pistons, and on the bones.
He uses bones that are constrained to make the spring stretch.
He uses three techniques to rig a tank tread, Modeling, rigging and animating them.
He goes over the basic idea of rigging with a basic setup. He sets up a wing rig with constraints, and also how to make a transformers like arm weapon action by moving one empty. He shows how to use bone constraints. He also shows how to use the action section in the dope sheet. Fake user stores the information in the blender file.