Image by Chris Klein Summer Beckons on the Boston Harbor Islands Even though summer is only days old, the word "staycation" has already earned the honor of being the season's most annoying buzzword. But if $4-a-gallon gas and the shaky economy does have you rethinking that trip to the Cape or "the islands" (a.k.a., Martha's Vineyard and Nantucket), you'll still be able to find plenty of island adventures close to home at the Boston......