This would be a bit out of the way from Harrisburg, but when I lived in York I used to go to Mr. Steve's
which is still my favorite home brew shop. I live in Philly now, but any excuse I can make to be in the York area I try to stop in and pick a few things up. The staff is super friendly and helpful and the store is pretty large so there's usually everything you need available. Again, kinda out of the way, but well worth it in my opinion.