Living in Baltimore, I can wax rhapsodic about all of the great places to get a tasty brew around town, especially from local microbreweries. But if you're only here for a weekend and you're looking for a huge selection and a solid menu of standard bar fare, you have to go to Max's Taphouse in Fell's Point. With over 100 taps (108 at last count) and a huge bottle and can selection, it goes without saying that if you can't find it here, you probably can't find it anywhere.
Everything at Max's is served pub-style: you place your orders for food and drinks at the bar, and whether you take a perch there or go to one of the many tables, your food will be brought to wherever you are. (The drinks you'll have to ferry back yourself.) The scene here can vascillate from quiet to rowdy fairly quickly, and be warned that Sundays during the regular NFL season can be extra-crowded.
737 S Broadway
Baltimore, MD 21231