h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

With a decent-sized didjeridu you can give the most fantastic massage. It's all in the vibrations.

The person being massaged should lie face down and have lots of space around them. Try and choose a quiet spot. Once they're relaxed, begin a drone away from them and move the didj in until it's almost touching their lower back. Throughout, try to keep the didj as close to their body as possible.

Move up the spine and across the shoulders, and down the length of each arm. Most people store all their tension in the shoulders, so linger there. If you can hit the right drone, you'll actually hear their muscles relax (the sound bouncing back to you will get softer).
Circle the head (a good chance for some swirling sounds) and move back down the spine.

By this stage, the one being droned will probably be unable to tell where you actually are as their whole body will be tuned into your didj. Just go with the flow.
It's nice to concentrate on the soles of the feet and the top of the skull (this allows you to squat or sit - particularly handy if you've got a heavy didj). If you're into chakras, concentrate on them.
Don't be surprised if s/he falls to sleep. It's that relaxing.
Finally, try to bring them round gently - a tibetan chime or some sort of bell is good.

One final note - if anyone gets really good at this, can they come and do me? I've sent shedloads of people off to vibrational Nirvana but never been on the receiving end...