Practical Information

The official money of Cuba is now the Cuban Convertible Peso, or CUC. The US dollar is no longer in use. They're also called "chavitos."  You'll need to change your money at the airport, a bank  or at your hotel from your national currency. Anyone bringing US dollars is going to take an extra 8-10% hit in addition to the fees for converting the foreign currency at the bank or cadeca. It's best to use the official money exchange venues as counterfeiting and theft is not unknown.
They're another type of money in circulation called "moneda nacional." If you do not have Cuban friends it's unlikely a tourist would have occasion to use the non-convertible peso, which is valued at about 20-1 to the CUC. A common scam is paying in chavitos and getting nacional in return.

Another common scam is to take a one CUC bank note and add a zero behind the one to make it look like a 10 CUC bank note.  The scammer then looks for a tourist to help him (or her) to make change and the tourist gets stuck with the doctored note.  ALWAYS make sure that any 10 CUC notes also say Diez on them and not UNO!!!