Central banks, commercial banks, development banks and other financial institutions are widely available in African countries. Banks are generally open from 9am to 3:30pm Mondays to Fridays, and 8:30 am to 11pm on Saturdays. Usually banks in airport site would adjust their business hours to accommodate international flights. Automated Teller machines are available in most large towns all over the cities. International banks have also branches in the major cities. All major credit cards are can be used.  However in some parts particularly in small towns you should have cash in hand.
South Africa's 'big four' banks

• Absa Bank
• First National Bank
• Nedbank
• Standard Bank

Foreign exchange services
These and other financial services are offered by South Africa’s "big four" banks as well as the credit card firms listed above. Other foreign exchange dealers in South Africa include the following:

• ABN AMRO South Africa
• Bank of Baroda (SA branch)
• Bank of China (SA branch)
• Bank of Taiwan (SA branch)
• Barclays Bank South Africa
• Bidvest Bank/Rennies Foreign Exchange
• Calyon Corporate Bank (SA branch)
• China Construction Bank Johannesburg
• Citibank South Africa
• Commerzbank (SA branch)
• Deutsche Bank (SA branch)
• Habib Overseas Bank
• HSBC South Africa
• Investec South Africa
• JPMorgan Chase (SA branch)
• Master Currency
• Meeg Bank
• Mercantile Bank
• Société Générale (SA branch)
• South African Bank of Athens
• Standard Chartered Bank South Africa
• State Bank of India, South Africa
• Tower Foreign Exchange

West Africa

Central Bank of West African State or the Banque Centrale des États de l'Afrique de l'Ouest (BCEAO). This seves eight west African countries. Benin, Burkina Faso, Cote d’Ivoire, Guinea Bissau, Mali, Niger, Senegal, Togo.

Central Africa

Bank of Central African States or Banque des Etats de l'Afrique Centrale (BEAC). This is a central bank that serves six central African countries such as Cameroon, Central African Republic, Chad, Equatorial Guinea, Republic of Congo and Gabon.

South Africa

South African Reserved Bank also known as Suid-Afrikaanse Reserwebank. This is the central bank of South Africa. Presently governed by South African Reserved Bank Governor Tito Mboweni.

Kingdom of Morocco

Bank Al-Maghrib- founded in 1959 and located in Rabat, Morocco. This is the central bank of the kingdom of Morocco. In 2008 Bank Al-Maghrib holds reserves of foreign currency with an estimated value of USD 36 billion.

Mauritius

Bank of Mauritius- that was in September 1967 when this bank came to its existence. Known as the central bank of Mauritius and a replicate of the Bank of England and was effective through the assistance and aid of the senior officers of the Bank of England.

EGYPT

Central Bank of Egypt- this is the central bank of the Arab Republic of Egypt located in Cairo. Governed by Dr. Farouk abd El Baky El Okdah. One of CBE obligation is to Regulates banks and the banking system of Egypt.
References:

http://en.wikipedia.org/wiki/Central_banks_and_currencies_of_Africa
http://en.wikipedia.org/wiki/List_of_banks
http://www.southafrica.info/travel/documents/      
http://www.southafrica.info/travel/advice/currency.htm