Spice Jars (I got mine from Williams Sonoma but you can get cheaper/different ones)
Magnets (Mine are from K&J Magnetics)
Dremel or Drill
Measuring tape (if you're anal about measurements)
Epoxy or superglue
Step 1: Preparation
I laid out my magnets on my spice jars. The tops are metal (steel?) so the magnets stick, but you want to make sure that your magnets are all pointing the same direction.
I also made a quick and dirty template for drilling my holes by tracing the bottles on a piece of cardboard and stabbing it with a knife.
Step 2: Tracing Holes and Drilling
I used the burr setting on my Dremel in order to make short, shallow holes wide enough for the magnets and deep enough for the magnets to lay flush once they're glued.