I just watched this video...

http://www.youtube.com/watch?v=LXGtE3X2 ... u_in_order

and it mentions that the suppression diode (reversed, and in parallel to say, a motor) allows the inductive energy to move through the diode, back to the power supply, and also returned to the motor where it will dissipate.

I can see how the motor might waste some current, but how does the current flow backwards to the power supply?

As a motor is a series of coils that is switched on and off to make the motor rotate.

You need to look at what happens when a coil is energized and then switched off.
When power is removed from the coil the magnetic field collapses creating a large voltage spike of reverse polarity.
The Diode helps to shunt this spike back into the correct supply rails as well as back through the motor windings.
Without the diode you would get large spikes of reverse voltage travelling back down the supply rails and reaking havoc with your circuit.

If you have a neon globe like the ones used for a indicator light on a stove or in a kettle or some 240v appliance (small glass bead with 2 leads ), and wire it across a relay coil (without the resistor on the neon), then energive the relay and switch it off, you will see the neon flash, as a neon needs around 100 volts to flash it, you can see there is a high voltage generated by the coil.
Now place a diode across the coil...........repeat test and ..no flash.

Pete.