This map by the Information Geographies project at Oxford Internet Institute shows us countries represented by their Internet population. The darker the red, the higher the percentage of that country's population that's online.

Fact is, there are many countries that are growing fast. Information Geographies notes in their findings:
Some African countries have seen staggering growth, whereas other have seen little change since we last mapped Internet use globally in 2008. In the last three years, almost all North African countries doubled their population of Internet users (Algeria being a notable exception). Kenya, Nigeria, and South Africa, also saw massive growth. However, it remains that over half of Sub-Saharan African countries have an Internet penetration of less than 10%, and have seen very little grow in recent years.
[Information Geographies via The Atlantic]