On a budget, Lexington & Concord Day-Trip still earns its price.
Mostly free sites; car/gas needed
For history lovers, the most meaningful day-trip from Boston — standing on Lexington Green, walking Battle Road, and pairing it with Thoreau's Walden Pond or the Alcott/Emerson literary homes is quietly powerful. The catch: it really needs a car, the sites are spread out and low-key (fields and monuments, not spectacle), and it's a flat experience if you're not into the history.