Sauder's is a Mennonite-owned dry-goods/meat/lots of other things store outside of Seneca Falls, about a 55-minute drive from Rochester. The variety of products is incredible--every kind of flour you can think of, spices, grains, home-style candies, baking necessities (soda, yeast, cocoa, brown sugar, etc.)--all neatly bagged in different sizes and on the shelf. They also have a deli (I'm not a meat connoisseur, but apparently you can get German specialty meat that is hard to find), inexpensive cheeses, fruit preserves, home-made syrups...the list goes on! Here's my best price summary: their big bulk items (50 lb bags of sugar, beans, etc) can generally be found for less at other places (Aldi, LDS Storehouse), but Sauder's prices for baking supplies are hard to beat (and they sell them in hard-to-find quantities).
Even aside from all practical matters, Sauder's is a very fun place to visit. The distance is a drawback, but it's one exit away from the Waterloo Factory Outlet Stores, so you could definitely make a day of it (the flour picture is just a random one I found online, but Sauder's is so great I thought it deserved a graphic).