The Zambian Kwacha is the local currency. It exchanges at around ZMK 5,000 to the US Dollar, which is the most commonly accepted foreign currency within Zambia.
VISA cards (both credit/debit) are readily accepted within Lusaka and Livingstone. MasterCard is still more limited in its acceptance. Outside the main centres it is best to use cash (travellers cheques are increasingly expensive to exchange).
Note that when using US Dollars, it is best to obtain brand new notes, or notes that are in the best possible condition. Also ensure they are post 2003, with large "faces". Old notes or damaged notes will either not be accepted, or may be accepted at a much lower rate of exchange.
Kanyemba Lodge accepts payment in most major currencies, and also accepts payment by VISA.