Skee hit on the main spots, but I'll elaborate a little bit.
First off, you have to go to Max's. They have about 100 different taps (more if you count the duplicates upstairs and in the side bar) and the selection is always amazing. The only thing is that the crowd on a Friday or Saturday night makes it a little bit less fun. I'd go on Thursday, or Saturday during the day (or both). Actually, I just got their weekly email saying that on Thursday they're putting 14 different Mikkeller's on tap. Need I say more?
The Pratt Street Ale House is a good brewpub if you like English Ales. They've renovated recently and Steve the brewmaster makes some great stuff. I'd also check out the Brewer's Art, which is a Belgian style brewpub and a fantastic restaurant. They have a pretty sweet bar in the basement that also gets crowded on the weekends, though.
Heavy Seas is a full-scale microbrewery just outside of the city. They do Saturday tours that you still might be able to get in on if you're interested.
Another local bar with a good selection is Mahaffeys (mahaffeyspub.com) . They have about 20 taps and a beer engine, but the prices are hard to beat and the people are always great. During happy hour (until 7pm), you can mix and match 3 10-ouncers of all but the highest alcohol drafts for $5.
There are other brewpubs in the suburbs as well. DuClaw, Red Brick Station, and Pub Dog are all hit or miss in my opinion. Flying Dog brewery is up in Frederick but that's a bit of a drive and I don't think they're giving tours right now. Victoria Gastropub in Columbia is a very nice restaurant with a good beer selection, but you'll probably pay closer to DC prices.
As for food... if you want Seafood, I'd avoid Phillips at the Inner Harbor. There are a lot of good places in Fells Point and in Canton that have seafood and aren't nearly as much of a tourist trap. Mt. Vernon (up Charles st.) has a lot of really nice restaurants as well.
Anyway, enjoy your trip! If the Orioles were in town this weekend you could walk up and get great seats for $10 and watch the visiting team win.