The Museum of Natural History is pretty awesome. I think the megaladon jaw display has since moved, though. Ya missed that. Next door is a huge art gallery/museum with a beautiful garden outside.
Both are free/accept donations. The Butterfly thing is the only thing that costs money to see.
FL Museum of National Historyhttp://www.flmnh.ufl.edu/
Grossology sounds pretty sweet, for the kid in all of us.http://www.flmnh.ufl.edu/exhibits/upcoming.htm