Modern Cottage has a great post with instructions for creating numbered cork coasters. You could alternate the numbers for letters or a symbol. The post explains how to create the number stencils for your coaster using freezer paper, varnish, an iron and a sharp xacto knife. If you wanted something instead of numbers you could easily make different stencils using the same instructions. We think using the numbers is best because it makes us think of the awesome Numb3rs tv show. (via Craftzine -> Whip Up)
Modern Cottage has a 