Compared to lions and tigers and cheetahs, for which there are a number of good exhibits across the country, leopards and snow leopards get shortchanged with subpar exhibits. Jaguars and pumas, from my experience, are somewhere between the two.
I think this is mainly due to the incredible climbing ability of leopards and snow leopards and the virtual necessity of completing enclosing their exhibits. I have seen a few open top exhibits (example Out Of Africa in my state of Arizona), but these are very few indeed. Some US states actually mandate closed tops in their state laws. As a cat fanatic, I find this situation somewhat depressing and I wish zoos would do better for these fantastic felines.
Since I assume your thread applies to common leopards (and not snow leopards), here are the very few good ones I know of:
USA
Out Of Africa
The Living Desert
Minnesota Zoo (maybe - not personally seen)
Staten Island Zoo (maybe - currently under construction)
Philadelphia Zoo
FRANCE
Le Parc Des Felins (4 distinct habitats - black leopard, amur leopard, sri lanka leopard, persian leopard)