Can a soprano's voice really shatter glass?

Theoretically, yes. Wine glasses each have a natural frequency - the ringing note you hear if you clink one gently. If a singer picks exactly the note that a glass resonates at, and sings with enough intensity, her voice will cause the air molecules around the glass to move causing it to vibrate in sympathy.

If the glass has a microscopic flaw or weak point, the vibration could cause it to shatter into pieces. The singer's voice would have to be extremely loud, and the glass very fine and delicate, however. Strangely enough, it's the same technique that dentists use when they scale and polish teeth using ultrasonic sound waves!