American Visionary Art Museum in the trendy neighborhood of Federal Hill.
We also brought our bikes and rode the Gwynn Falls Trail that winds through West Baltimore. It isn't completely closed off from the rest of the city as there is a dumping problem in the adjacent river and many abandon buildings are collapsing within a stone's throw of the trail.
There is now a Google Maps link on the left that shows all the places (restaurants, museums, physics labs, etc.) we went while in Baltimore, we'll keep updating it as we travel.
Baltimore is a strange place. We have been watching the HBO series The Wire which chronicles many facets of life in Baltimore, from cops and drug dealers to politicians, the school system and the newspapers. Compared to many large American cities, it has yet to be gentrified to any extent and thus retains a relatively low cost of living.