A friend I work with brought this up today and I decided to check it out: I-Doser.com
Basically, it's a sound player that plays a unique sound that allegedly stimulates special brainwaves in order to achieve an altered state. Depending on each sound's title (for instance "alcohol") you should experience a similar sensation to it if done correctly.
In order to prepare, you must literally remove any distractions surrounding you, relax completely, and turn off your mind. Likewise, for you "recreational" drug users out there, this sould be an easy task. (I smoked before I tried it - works