What could cause a vague aching sensation in my legs after a night of hanging out and drinking alcohol? it's mostly noticeable in my shins and calves.

Vague indeed: Electrolyte imbalance (hang over) , trauma not recalled, lactic acid build up for what ever reason (excessive standing, walking or even passing out with one leg pinned under the other) or spending too much time on a bar stool resulting in compression of the sciatic nerve. At age 26 you are a bit young to develop alcoholic neuropathy in the absence of any additional condition (diabetes, B vit low)