J&J Alterations & Cleaning, on York Rd., in Lutherville (so a little north of Baltimore). I get most of my minor alterations done there, and can recommend them for that. They do a decent job on dry cleaning, too. Roughly 100% better than, say, nearby Zips.
'Course, saying a place does a better job than Zips is faint praise, indeed. But to be fair, Zips has inexpensive "in by 9, out by 5" service, while J&J requires a few days turnaround time.