Mani Wheels made out of Altoids Tins
Tibetan prayer wheels contain mantras written on strips of paper. Spinning the prayer wheel is like saying the mantra repeatedly. Traditional prayer wheels contain hundreds, thousands, even millions of copies of the mantra "Om mani padme hum." evoking Chenrezig, the Bodhisattva of compassion (Avalokitesvara).
Smaller prayer wheels are turned by hand. Others are powered by water wheels, hot air raising from candles, or the wind. Prayer wheels are spun clockwise when looking down on them.
Turning a prayer wheel is like chanting the mantra "Om mani padme hum" (Jewel in the Lotus of the Heart). Reciting this powerful mantra builds positive karma, evoling the Buddha of Compassion (Avalokitishvara).
Basic background material can be found on this site. This is a detailed overview of the tradition. Lama Zopa Rinpoche speaks on "Advice on the Benefits of Prayer Wheels".
I use a traditional prayer wheel but I like making things. Quirky, personal, recycle art, DIY homebrew geeky stuff. The idea of digital prayer wheels attracted me the first time I stumbled across the concept. A perfect example is this Internet prayer wheel setup as a memorial to internet pioneer Jon Postel. Another approach is this digital prayer wheel. As simple as it is this webpage is a digital prayer wheel too. Inspired? Try building your own.
While we're on the subject of digital prayer wheels, the Sakya Monestary here in Seattle claims to make the world's most powerful prayer wheels. They contain 1.3 trillion (with a "t") mantras and sutras on a set of DVD's. This article has background on the Sakya Monesatary prayer wheels as does this piece from Earth Sanctuary. The Nyingma Institute in Berkeley makes more tradional prayer wheels in a modern manner. Others are build prayer wheels full of microfilm.
Being a nerd, I make prayer wheels out of empty round Altoids tins. This YouTube video shows how I do it. I use keychain parts and a bolt for the counterweight. The mantra is printed, cut into strips, and glued into one long strip. The strip is coiled up and placed inside of a round Altoids tin. A replacement garage door roller is glued on as a rotating handle.
I met someone who asked for help making her own prayer wheel. This page is about Carolyn's prayer wheels.

The parts include a replacement garage door roller, an empty Altoids tin, and misc. hardware.

The mantra is printed and then cut into strips which are glued end to end.

A third hand helps with the final assembly.

