I think there are quite a lot more sites than the 3 already connected -eg Oudane etc in Mauritania. But I soon ran into definitional problems about where the Sahara starts and finishes - Altantic to Red Sea, Mediterranean to ...? the southern boundary seems generally to be regarded as being defined by an "isohyet of annual precipitation" - but at what level there seems to be some debate.
But parts of N Africa eg the hills of Cyrenaica, the High Atlas are clearly not "Saharan".
And what about the Nile Valley?
I personally would have regarded some sites I have visited as being Saharan albeit at the "edge" eg Timbuctoo (near the Niger but part of "Saharan culture") and "Gebel Barkal"
Djenne?
I have looked hard for a good map which doesn't just "scatter" the letters "S.a.h.a.r.a" acorss the middle of North Africa! The best i could find was
http://encarta.msn.com/media_461520504_761560427_-1_1/sahara.html
Could we use that? (Djenne is outside by the way whilst Timbuctoo is inside! All of the Nile Valley sites are inside)