What Sheryl Sandberg said in her HBS speech

Speaking at Harvard Business School's Class Day, Facebook's COO barely addressed the controversy over the company's IPO.

FORTUNE — Facebook COO Sheryl Sandberg was the keynote speaker this afternoon at Harvard Business School's Class Day, which precedes commencement. Days after a tumultuous May 18 initial public offering, the social network has come under a barrage of questions and criticisms which could have made the event, well, awkward.

So what happened?

Not a lot. MORE

The technology behind bike sharing systems

Sharing a bike with a friend requires trust and a U-lock. Sharing 600 bicycles with the city of Boston requires technology and a big investment. Alison Cohen's Alta Bicycle Share is up for the task.

Alison Cohen used to ride her bike 17 miles to work every day, a "ridiculous commute," she now admits, but one which gives her solid cred in her current job: president of Alta Bicycle Share, a MORE

Moving beyond coal. Maybe

What are the keys to leveraging alternative sources of energy and moving beyond coal?

By David Whitford, editor-at-large

Bill Weihl, Google's (GOOG) energy czar, suggests two new ideas: Encourage new technology through investments in R&D; and "generate market pull" with consumer incentives plus government procurement mandates. Can we get to low emissions without nuclear? "Probably," says Weihl, "but I hate to take it off the table."

Mike Morris, CEO of American Electric (AEP), one MORE