Yeah, I'm fortunate where I live that there are many teams at many different classifications/levels that are within about 2 1/2 to 2 3/4 hours of Harrisburg that one can go see for a day trip without too much inconvenience:
AAA (1) - Scranton/Wilkes-Barre
AA (6) - Harrisburg, Reading, Bowie, Trenton, Altoona, Binghamton
high A (3) - Frederick, Wilmington, Potomac
low A (2) - Hagerstown, Lakewood
short season A (3) - Aberdeen, State College, Williamsport (both Staten Island and Brooklyn are just beyond that threshold)
Heck, even a number of independent minor league teams, most notably Lancaster, fit into that criteria as well.
Of course, in the majors the Orioles, Phillies, and Nationals are within 2 hours, the Yankees and Mets are within 3 hours, and the Pirates are just over 3 hours away too.
(P.S. I've seen each of the aforementioned teams, excluding Staten Island and Brooklyn, at least once in their home ballparks.)