Anthony Corrado (appearing live from a new video studio in the Lovejoy Building) explains who super delegates are, how they came to be, and how they may affect the Democratic nomination.
http://www.pbs.org/newshour/bb/white_house/jan-june08/superdelegates_02-19.html

For more Corrado commentary see:

Morning Edition (NPR), February 20
In 2008 Campaign, Money Isn’t Everything

The New York Times, February 17
Registration required.
Show Me the Delegate Rules and I’ll Show You the Party

USA Today, February 17
Clinton campaign accuses Obama of ‘flip-flop‘”

Providence Journal, February 17
Democrats’ fate in the hands of the super delegates

USA Today, February 15
Dems stumped figuring Fla., Mich. into delegate equation

Financial Times (UK), February 15
Clinton and Obama eye Wisconsin