What makes a wine glass sing?

A wine glass makes a noise when you run your finger along the rim because of vibration. Your finger rubs against the glass and sets up vibrations because of friction. The glass crystals are "frozen" into a solid and are lined up all in one direction inside the glass. When the rim vibrates, the ripples spread all over the glass, and the bell-shape of the glass focuses the sound back out the top. Voila - sound.