9am unless it is Sunday. If you are in dire need of libations, drive to Salem, NH or Plaistow, NH. You can "Live Free or Die" there much easier than those of us in Boston. In New Hampshire, alcohol is sold pretty much everywhere (gas stations, pharmacies etc.).
And Kappy's (a Boston staple) apparently will deliver to your party: http://kappys.com/oncall.html
Here's my local stop: http://www.insiderpages.com/b/3715351478/mc-donoughs-liquors-wakefield
And a "wicked" cute wine shop near me: http://nastynonnis.com/