Boston Harbor has many cruise lines, one of the best for the money, is www.massbaylines.com  You can purchase tickets behind the Boston Harbor Hotel just up from Long Wharf. at 60 Rowes Wharf or call them at 617 542 8000    

Another boat to try for cheap is the local MBTA Ferry.  You can take it to Quincy, Hull, Nantasket, Hingham, Logan Airport, Charlestown...each way is $6 or $3 if you are disabled.  Plus they sell drinks and food onboard and the views are spectacular.  Take the ride that goes out at sunset and there is your sunset cruise for $6 bucks! Go online at    http://www.mbta.com/fares_and_passes/... .  You can also get a boat to go whale watching or fishing or to the cape and the islands by going to MASS STEAMSHP AUTHORITY   http://web2.steamshipauthority.com/ss...    or call them at 877-623-6846   Here is another page which explains all of the boats and water taxis you can take and where they go  http://www.massport.com/logan-airport... 

When you need to travel just up the street or even over to the other side of the city you can forget the taxi and take the "bike rickshaw";   it's a company called BOSTON PEDICAB and it's great. They get to ride on the street and you get to see everything with the breeze as the a/c; the views are spectacular!  Park your car somewhere and call them for a ride at 617 266 2005  or go to  http://www.bostonpedicab.com

During the summer the BOSTON HARBOR HOTEL has free offerings including a different kind of live band, blues, swing, oldies, etc. Friday night is movie night...go to  bhh.com for the schedules.  Also CITY HALL PLAZA has outdoor concerts for free as well as the HATCH SHELL ON STORROW DRIVE. Go online to get schedules. Summer is fun and much of it is free in Boston!