With 10 home games left, I thought I'd mention a fantastic hamburger vendor outside Camden Yards. Big juicy, and well-seasoned, they're some of my favorite burgers in Baltimore. $3 if I remember correctly (with some kind of chips & soda deal). MUCH better than anything inside the park.
If you're facing the stadium from the north, he's on the right of that fenced-in parking lot where various and sundry vendors are lined up. I believe he's the only guy out there grilling hamburgers and hot dogs.