Dreamachine

image: Wikipedia

More info and an online Dreamachine here.

I've used one of these before and they work. The online version is even more potent.

Please note: This online Dreamachine can trigger seizures for those with Photosensitive epilepsy, depending on the frequency chosen, so be careful. I just liked the picture. (Which appears to be William S. Burroughs and some unknown individual.)

via Mogadonia