The Lloyd Center for the Environment is a great place to wander the trails and investigate the Nature Center's exhbits.  They have a saltwater touch tank and 5 miles of trails to hike on.  Check out the amazing view from the Pilot House - it was designated one of 15 Special Places in Massachusetts by the State.  They have great summer camps and school programs for kids too!  Take a look at their "creature feature" section of their website - a great learning tool for kids.