Oh I have day trips for days lol
Not too far from Negril:
Percy's Retreat
Blue Hole
Mayfield Falls
Montego Bay Area:
Rocklands Bird Sanctuary
Glistening Waters
Ocho Rios Area:
Mystic Mountain
Dunns River Falls
Tour Port Antonio (But this would be too far for a day trip)
Kingston:
Bob Marley Museum (but would also be probably too far for a day trip)
Blue Mountain Tours
I have done most of these listed but out of all so far my favorites have been:
YS Falls
Pelican Bar
Glistening Waters
Mystic Mountain
Bob Marley Museum
However, I am REALLY looking forward to the Rockland Bird Sanctuary which I have yet to visit