There are a lot of great places to see in Baltimore - Laura Lippman actually did a round-up on her website in September, covering the restaurants. You might want to check that out. http://www.lauralippman.com/
The Inner Harbor is great, very tourist-friendly. The Barnes and Noble down there is one of the most original bookstore buildings I've seen.
Since moving here I've done a lot of the touristy stuff - the aquarium, the duck tour (which takes you by Edgar Allan Poe's grave) and stuff like that. I'm not sure which dates you'll be in the city but Sept. 26-28 is Baltimore's Book Festival http://www.baltimorebookfestival.com/index.cfm?page=plan and you might want to check that out.
Then again, it's the same day as Washington's, so you might prefer to go there.
And if you're still around the area October 1 you really should try to head to Washington, as Ian Rankin has a signing there that evening.
If you're interested in the Baltimore of The Wire and Homicide, you'll see lots of familiar things easily enough. I'll ask Brian when he gets home if he can think of more specific things to see and do - we're probably going to the book festival ourselves.
I did have a chat with Steve Mosby, who was as lovely in Harrogate as in Bristol - top bloke indeed. And of course it was really good to meet you too. I can’t remember whether you said you might be able to make it to Reading in September?
08's not been a bad year so far, long may it continue! I hope your move goes well, and you get plenty work in on your novel while your offline. Just think, you'll have a whole month of my nonsense wittering blog to catch up on when you're back! (grin)