If you don't have a glass cutter you can soak yarn in acetone. Tie the acetone soaked yard around the bottle tightly, hold it over a full sink of water, light the yarn with a match and the bottle comes clean apart. bottles of various sizes can be used to make lanturns. They look beautiful!
My BF & some friends want to do this (I've been saving bottles!) - we've found lots of sites that say to dunk the bottle in a sink of ICE water after the yarn is lit & burned around. Also, to rotate the bottle as the yarn burns. I haven't actually tried it yet but I'm looking forward to it!
Then I found a cool project for the tops (that I think someone mentioned already) - make wind chimes out of them! Use some heavy gauge wire to string the tops together and use bottle caps & large beads for spacers. Not recommended if you have pets or high winds!