There is Cactus Dan's Youtube Page which has some good stuff, but I was wondering if there has a manual or instructions of any kind for the different tools?
If no one does maybe we can start a community writing of instructions for Cactus Dan's tools on this thread.
I'll start with what I know
Holding Ctrl before clicking on many things can bring up additional options before being applied.
CD Add Spring Constraint - Makes a spring between two non joint objects. If used on joints they seem to fall forever. Use on two controllers to get springiness.
CD Add Spline Constraint - Constrains an object to a spline path. Constrained object can be moved via a value or dragged with the cursor.