There's one in Canton that we like. The Anchorage.
http://www.anchoragemarina.com/Canton's a little bit of a walk from Horrible Place (which, to me, is a good thing). There is the water taxi. We typically walked over to the Harbor and then took the taxi back. There's a huge Safeway grocery store about 3 blocks away and a number of decent restaurants and pubs.
Closer is the marina at the Henderson's Wharf hotel in Fells Point. Stayed there when we had the in-laws staying in a room at the hotel. A bit on the sparse side regarding boating features (the anchorage has a pool out on the docks) but very convenient to Fells Point.
I prefer not to stay up in the Harbor itself. Way too much foot traffic and noise for my liking.