I was there a few years ago, so I'm sure there is more to do than when I was there.
At any rate, I would suggest checking out Eutaw St and the clubhouse store while you are at the ballpark. If it's you first visit there, you can also get a "My First Game at Camden" certificate at gust services.
While you're in the area (but a few blocks away from the ballpark), I would HIGHLY recommend checking out Faidley's Seafood in the Lexington Market ( 203 N Paca St, Baltimore, MD 21201) if you are into seafood. The crab cakes were amazing, as were the GIANT oysters at the oyster bar. Also,very reasonably priced for what you end up getting.