Wikipedia says in its entry on Al Azhar University in Egypt that "Jewish philosopher Maimonides delivered lectures on medicine and astronomy there during the time of Saladin."
The source given is volume 13 of the Muqarnas journal. It is not available online for free, but it can be found is in this article by Nasser Rabbat.
I cannot find any Jewish sources for this assertion. I did find it mentioned in passing in this Arabic article. (People also claim that Maimonides lectured at the University of al-Qarawiyyin in Fez, Morocco.)
Does anyone know the source for this? It doesn't seem to be too far-fetched but it could easily be a Muslim legend.