Wife and I Will be in Lancaster, Pa for the 4th of July. Besides lancaster Brewing and good recomendations. We are staying Downtown.
Check out The Fridge and The Friendly Greek for bottle shops, in addition to the aforementioned visit to Spring House
Definitely Spring House, also out by F&M College is Iron Hill (lots of their beers on draft, usually anywhere from 12+, many quite tasty and very good food) and Hunger & Thirst (excellent if small tap list, about 16 drafts, nice bottle shop and provision store), also if you're in the mood for some excellent dining and usually a nice selection from their 6 or 8 drafts check out John J. Jefferies.
If you head North on Rte 272, you'll find Stoudts Brewery in Adamstown. It's less than half an hour and well worth the trip. There's also Rumspringa in Intercourse and St. Boniface in Ephrata, both within 20 minutes.
Spring House is a must hit, in my opinion. As well as Hunger-n-Thirst; Andrew and his staff will take great care of you there. Nice draft list, great bottle shop and an awesome provisions store. I'd also recommend Iron Hill. Personally I think The Fridge is a little bit pricey but it is worth checking out as it's in the same general area.
Lancaster and evnirons is awash with good beer. Fridge, JJJeffries, and Hunger-N-Thirst are TV free, if that makes a difference. Also a 17 minute walk from Fridge to H-N-T. Shorter walks downtown will take you to Federal, Pickle Bar, Annie Bailey's, as well as those mentioned above.
If you're willing to drive/there for more than just one day, and just checking out beer or something, there's also Stoudt's Brewery and Rumspringa (which is small, but part of the experience). Again, Spring House for sure.
Spring House downtown, Iron Hill always has solid offerings, Stoudt's is about a 20min drive North but worth the trip, great food, beer and atomsphere. St. Boniface is another good one, and if you trip to Boniface, you're not far from Union Barrel Works in Ephrata. Bube's is hit or miss but not too far out of town. If willing to drive a little farther, Troegs and Victory are about a 45 minute drive away.