GM closed at $2.92 a share, their lowest level in more than 60 years (December 2nd, 1946 to be exact). I can't even find the data going back that far, but this chart shows just how far things have come.
Amazingly, GM is now technically a small-cap stock according to the WSJ:
Since the company’s market capitalization has roughly fallen in half in a week, the once proud Dow component is now below the $2 billion threshold used by many Wall Street trading operations to denote the difference between a small cap and mid cap.
Data Source: Yahoo