MyNoise

I'm sure it's available everywhere.

It's called myNoise, and the ones that I like the best are the, um, the Tibetan Monk soundtrack, and then there's also a binaural sound generator where you can adjust the, um, difference between one frequency and another to where the difference between the two becomes a frequency in and of itself.

So you can adjust it to four, five, six, seven, eight hertz, and it will entrain your brainwaves.

I find it very relaxing.