I didn't know what these were called, so I googled "stone balcony supports" because that is what they are and the web is as good a place as any to start.
Google led me to wikipedia, which is the best substitute I have found for my long-absent Grove Dictionary of Architecture. There, I found an article called simply "Corbel", which I recommend if you'd like to know more about architectural application, significance and engineering realities of these features.
My primary interest lies elsewhere. I'm more interested in the creativity and craftsmanship designers of stone and concrete have thrown at these support structures. Collecting images of corbels around Beirut is my new pet project and as such you'll be seeing lots of examples of them right here in the coming weeks. I hope you'll enjoy it as much as I will.