The African Union celebrated its 50th Anniversary last year and is the evolutionary body of the OAU, Organization of African Unity. (http://en.wikipedia.org/wiki/African_Union). The AU complex and headquarters is in Addis Ababa and Ambassador Brigety who is the Ambassador for the AU, frequently has meetings there, but is officially housed at the U.S. Embassy.
From what I could surmise, the AU is part European Union and part African mini-U.N. It seems to be more about continental cooperation and intra-government communication, and not currently involving a common currency and banking system.
The complex is new, stunning and was very educational - and we wanted to share a few pictures.