A bit of background first:
The Moon's orbit around the Earth gravitationally attracts the ocean just a teeny bit, causing tides to rise and fall in Earth's oceans, as we learned in science class.
Since the Moon and the Earth don't "run out" of gravity, and we -hopefully, anyways- won't run out of water, this is already, theoretically, a zero-point energy source feeding off of the (in human terms, anyways) perpetual motion of the moon's orbit around the Earth.
Problems arise, however, when you're nowhere near an ocean- say, in space, because space is cool.
This is what I propose to take advantage of tidal forces. However, since the human race hasn't cracked gravitics yet, we'll have to make do using magnets.
If you've ever tried to get a magnet to levitate on another magnet, you'll know that it's fantastically hard- the magnet keeps flipping 'round and sticking to the magnet you're trying to levitate it on.
One way around this is mechanical constraint- just fix the magnet on a pole so it is physically impossible for it to flip around.
A (presumably) very bored man named Roy Harrigan discovered another way around this - simply spin the magnet you're trying to levitate. Gyroscopic forces overcome the magnet's attraction to the opposite poles, leading to a perfectly stable spin that can go on for hours- at least until air friction acts enough on the magnet to slow it down and it all goes haywire. Remove the air, and you remove the friction. In a vacuum, the spin will go on forever. However, since there is no way to harvest rotational energy without incurring at least some friction, all you've got is an interesting office toy.
Well, there was no way to harvest rotational energy without friction. Turns out that we were all thinking about it from the wrong angle...
What if, instead of mechanically levitating just a magnet, you decided to put a payload on it? A payload consisting of very light ferrofluid and tide mills. (And yes, at this point, we're talking the mother of all Levitrons. Just thinking about it gives me goosebumps.) This would be our "earth" to paralell the earlier discussion of tides.
And, in lieu of a moon, a spinning magnet, set in orbit around the first. The magnetic forces from the second spinning, orbiting magnet would act upon the ferrofluid, dragging it back and forth like an ocean. This motion would be harvested by the aforementioned tide mills, and the mechanical energy from that translated to electrical energy via a garden-variety dyno. The electrical energy would be transmitted via the mechanical levitation no-flip pole(s) (one for + one for GND, naturally) and, eureka, easy electricity for eternity.
Building the "Money for Nothing" generator, as I've decided to call it, is another level entirely- one that I have nae the finances nor the time to commit to. Perhaps some brave DIY'er will decide to take it on.
That, and I'm not 100% sure this would work... it does violate the Second Law of Thermodynamics, after all.