It seems that we missed this news when it was announced a few weeks ago. JetBlue has announced that they will be operating flights from Boston to and from Nantucket beginning May 17th. This will be a seasonal service that will run through September 4, 2012. There will just be one flight daily each direction.
JetBlue has offered flights from Boston to/from Nantucket since 2007 through a partnership with Cape Air/Nantucket Airlines. However, this new service will be operated directly by JetBlue. It looks as though that partnership still exists. When searching for flights through Boston, there are flights to/from Boston offered by both JetBlue and Cape Air.
The JetBlue planes will be quite a bit bigger than the Cessna 402s that Cape Air uses. I know a lot of people get a little nervous when getting on the Cessnas, but I actually like flying on smaller planes. Have you flown to Nantucket? What's your preference?