Mali , what a country....
Maybe the most interesting in all Africa in terms of culture and people way of life and hospitality if you can spend some time with them and not stay too long with the expats.
The above posts are more or less correct, but if there is one place to see in Mali, you OUGHT to visit the Pays Dogon.
It's around 400kms east of Bamako to the south east of Mopti and then you can keep going toward Tombouctou, but I would put Mopti, number1 for an African experience.
If you can read French I would recommend "Le renard pale" of Griaule, you will learn amazing things about the Dogons.
Well, sorry guys this post may sound boring since there is nothing about aviation, but the ethnology of the Dogon people is for sure a must.