I can't seem to find a resource that explains how to do this. An example would be to take a cylinder that has been rotated whose plane is at a different angle from a cube and rotating it so the face of the end of the cylinder meets flat with the face of the block. Is there a reference in the manual or a YouTube somewhere?

Ok - I think I found it. Set the workplane to what I want. Select the object the alt+shift+W and the object aligns to the plane.