First... acquire your cogs... I got mine from inside a DEKAD alarm clock from Ikea (yeah... I like taking things apart)... but I think any wind up clock/toy would do. You could also buy a bulk of cogs from ebay or even from a hobby store if you're lucky.

Gather the rest of you supplies. If you want your earrings in a different color than the oldschool goldish one (black, white and bright pink are some that I would like to try), now is the time to spray paint them.
Then, lay out your design. I wanted mine to be roughly the same length, so I matched a couple of small cogs with a long clock hand and three bulky cogs with a short clock hand.

Time to put things together. I made some rings of wire to join the cogs and clock hand together, but where I couldn't do that, I used a softer wire to sort of "stitch" them together (hiding the end of the wire at the back). Then ad your earring hooks, and voilá, you have a pair of earrings :D