The currency is the Bahamian dollar (B$1), pegged to the U.S. dollar so that they're always equivalent. In fact, U.S. dollars are accepted widely throughout The Bahamas. Notes are in denominations of B$100, 50, 20, 10, 5, 3 and 1, and 50 cents. Coins are in denominations of 25, 15, 10, 5 and 1 cents.
You can change currencies at a local American Express or Thomas Cook or at your bank.
Most large hotels and stores accept traveler's checks, but you may have trouble using a personal check.