If you've got kids, go to the aquarium--great stuff, and in a scenic part of the city (albeit a rather manufactured section). Otherwise, Fells Point is a great old-school harbor area with fun restaurants/bars, while Little Italy has amazing Italian food.

Take a tour of Fort Mc.Henry.It lies in one of Baltimores oldest nieborhoods,coming and going,you can see more of what Baltimore is all about.

The National Aquarium is definitely worth a stop, though book ahead as it gets busy. There's also a WWII sub nearby. Another worthy Inner Harbor highlight is Camden Yards -- check out the ballpark, watch a game, and visit some of the baseball museums there!