Duc9 said:
These are all within walking distance for someone who rides. But, if you've never had crabs...
All of Duc9's recommendations are good. If you want steamed crabs, Bo Brooks is a safe bet (there are more authentic, neighborhood places, but I'm not sure that any of them would have crabs out of season -- Bo Brooks always has them). Bo Brooks also is in Canton.
The one thing I would recommend highly, if you are going to Canton or Fells Point, drive rather than walk. The distance is not that great -- 2 miles to Fells Point and 3 miles to Canton. But, there are some less than safe neighborhoods between Downtown and Fells Point and Canton. Also, Fells Point and Canton are east of Downtown, not north of it.
If you want to walk, the area just south of the Inner Harbor (Federal Hill) has lots of restaurants. I am not current on which one are good, but you would have lots of choices. Also, if you want to walk due north of the Inner Harbor on Charles Street, there are some good restaurants in the vicinity of the Washington Monument (about 8-10 blocks north of the Inner Harbor). One of my favorites is The Helmand, an Afghan restaurant. If you are in the vicinity of the Washington Monument during the day (the Walters Art Museum is near there and worthwhile to visit), there is a very small Thai carryout (Thairish) with three tables next to the Helmand that I also recommend. About 8 blocks further north on Charles Street (just north of the train station -- you would have to drive from the Inner Harbor) is a tapas bar that I like, Tapas Teatro.