If you are in the area and you are lucky enough to have a venue that lets you BYOB, you need to get yourself to Corridor Wine and Spirits, the Costco of liquor stores.
It is right off 295 in Laurel, and is an excellent place with a helpful and knowledgeable sales staff. Did I mention that everything there is incredibly cheap? Also, it's huge. They have everything. Cases of local microbrews, cases of cheap beer, expensive beer, the option to mix and match six packs, every kind of liquor imaginable, and then a wine section that is bigger than our entire liquor store here in fed hill.
You can also search their inventory online, to check their prices on wine (beer you have to call) and liquor. You can also fill your cart online and pick it up at the store, although I have not yet tried this feature.
We went over the weekend and picked up 2 cases (24bottles) of beer for $30 (so less than a dollar a bottle); plus I finally found Barefoot Vineyards Moscato in smaller bottles and I grabbed a bottle of their Mother's Day wine, Petals Riesling. It was pretty good, for a $7 bottle of wine (probably $10 anywhere else.)
Another idea that Mark suggested for stocking the bar was to go on vineyard tasting tours around Maryland and every time we find a wine we like, buy a case of it, and use that to stock the bar at the wedding. We're going to need backup on that one because I don't like reds, or dry wines. We will probably do that in the fall, but this Saturday is Wine in the Woods, for anybody looking for a good wine tasting experience.