They're really easy to make, look great and you can use any kind of air dry or polymer clay.
The air dry light I used is very odd, the finished result reminds me of polystyrene and it certainly is light. I quite like the effect. I decorated mine with sharpies, but actually I think if you were to use paints and varnish them you'd get a better result.
Here are some of the beads I made using polymer clay to give you an idea of how they'd look.
Clay (air dry or polymer whatever takes your fancy)
Skewer or toothpick for making the hole.
Take a piece of clay slightly larger than you want you finished bead to be and roll it into a ball.
With your craft knife slice a straight edge down one side of the ball. Then working from that flat edge another at a slightly different angle, then another. Keep going until your entire bead is made up of flat edges.
To pierce the hole, choose a side for it to start and insert your skewer, twist it slightly as go through the clay. Don't put it all the way through the bead, but instead just leave a tiny indent on the other side of your bead. Then insert the skeewer through the other side using your indent as a guide, carefully twisting as you go through again.
If using air dry clay, leave to dry as per the instructions, if using polymer clay, bake following the instructions on the packet.
When your beads have hardened, decorate as you please or leave them as they are, string them up and wear with pride.