If MD we always fish out of Bahia Marina. Nice bait shop, boat and rod rentals, head boats, charter boats you name it. Plus Fish Tales is an awesome bar and restaurant. If you're taking a boat they can tell you where to drift the bay for flounder. You can rent pontoons and they'll provide maps of where to fish as well. Any info you need they should be able to provide. Without a boat most people fish the piers and route 50 bridge. Head boats run charters for sea bass and flounder as well. Plenty of options depending on what you want to do.
OC MD? If you want a good captain, Nick Clemente (Get Sum Charters) flounder fishing in the bay. He's good at it and a great guy to fish with. Google him. I think he's like $400 for a 1/2 day w/ up to 6 people. If the blues are running the beaches, chucking salt water Krocodile spoons is great fun! You need a heavy spoon to be able to cast with the wind. Have fun!