A neat little app from linuxlabs.com that uses sound to shift the frequency that your brain is working at. This can make you more alert or put you into deep relaxation and meditation. You can vary the frequency and volume via the program directly or via a PDC script system. Also included in the package is a little app to convert your scripts into wav files to record to a CD-R (note that conerting to mp3 will not work as the harmonics and the l/r balance will be lost (or at the very least screwed). The site says that you need to use headphones to get it to work however I found that if you turn your hi-fi up loud enough then it has a similar effect (much to the disapproval of my neighbours). There are a few other prerequisites (a linux box, OSS compatible sound drivers and GTK 1.2) but other than that it should run on any system no matter the specs.
The hompage is http://www.linuxlabs.com/autozen.html