Walk the town. UMass is north end of town, Amherst College is south - the bulk of the town is between the two over a mile or so. There are tons of shops, coffee places, restaurants, some bars. It gets very rural quickly outside town in any direction except west towards Northampton on Rt 9 - that’s the shopping strip mall area, mainly. Northampton is very cool also, home of Smith College and a quirky hip city larger than Amherst. All women though, assuming you are male.
Puffer’s Pond is a popular swimming spot if you are there in hot weather 