Socrates and Plato
Renaissance / Reformation
Age of the Sutra
Buddhists and Jains
Slavery / Diaspora
Africana 20th Century
Grad studies on Arabic philosophy
How about Munich? But assuming you want to stay in North America the best option is probably Toronto, with Deborah Black and an array of talent in ancient and medieval. Notre Dame is very strong in medieval generally but doesn't have anyone who focuses on Islamic thought since my doctoral advisor David Burrell retired. Really you need to think in terms of individual scholars rather than programs when it comes to this specialization -- you aren't usually going to find more than one person, especially in a Philosophy Dept. So there would also be Richard Taylor at Marquette, Therese-Anne Druart at Catholic U, Jon McGinnis at U Missouri St Louis, etc. At Yale though they have Dimitri Gutas, probably the leading scholar in the field, albeit in Near Eastern Studies and not Philosophy; plus they have Frank Griffel who I believe is in the Religion Dept. And they are strong in Ancient in the Philosophy Dept. At McGill in Montreal there are Rob Wisnovsky and Stephen Menn though he's sometimes in Berlin.
In my opinion the field as a whole is stronger in Europe than in the USA.
I have more to say about this so if you want you can send me an email about it (firstname.lastname@example.org).