Two Minnesota-based companies are on BusinessWeek magazine's list of the nation's top ten corporate boards. The magazine gives the boards of Medtronic and 3M high marks for independence, accountability and quality. By comparison, Apple, Xerox and Gap all made the "worst" list. And the magazine reserved companies like Enron, Tyco and Worldcom for a brand new category called the "Hall of Shame." Business Week Management Editor Louis Lavelle says 3M and Medtronic are both newcomers to the "best" list: