Get out of Boston and explore the coast for a real change of pace.
Catch an early train from Boston to Cape Ann, get of at either Rockport or Gloucester. Time table www.mbta.com/schedules. Its about $20 including a bike.
I got off at Gloucester and headed South for Dog Bar Breakwater but missed the turn... it was foggy in the morning! Followed 127A to Rockport which is a great little stop. Then head North and look for Halibut State Park. There is only one little sign that says "state park" so is easy to miss. Nice headland for views and possibly an Atlantic path for a sea edge experience. Continue on the 127 and look out for the wooden bridge over to Annisquam - nice houses on the other side but all private. Its now only a short cycle to Gloucester. I continued on through Gloucester and headed West to Manchester by the sea... singing beach is very nice. In Manchester next to the level crossing 100m from the station stop is a great little cafe and 200m South of there is an ice cream shop called Captain something... I found both fantastic...
Basically the whole area is nice and you cannot go wrong... weather for me was changeable and the trains were only once every 2 hours for the return... I have done this trip three times and it is a great escape from city life.
If you have a car it would also be a top day out.