I am looking for an ad manager script/system (open source or paid) which can deliver different ads based on the IP - country of the visitors. Would be nice if you can name one if you know!
Use Google DFP it is the easiest way to do that
Watch the video and learn from it.. can't find a better resource
mySimpleAds has geo-targeting capabilities, but as the name implies it's not going to be a match for say, OpenX on features. It's worth a look if you don't have too much need for too much advanced stuff, though.