The national currency is the boliviano. As of January 2010, the exchange rate is generally Bs6.97/$USD. Bills come in denominations of 200, 100, 50, 20, and 10; coins are in 5, 2, and 1 bolivianos, and 50, 20, and you will find sometimes 10 centavos (1/100 of a boliviano). Bills larger than Bs20 can be hard to break, but a quick phone call or internet session at a Punto Entel (see Contact, below) will usually get you change.
Currency can be exchanged for US dollars and most South American currencies at casa de cambio agencies or street vendors. Expect to negotiate for a favorable exchange rate, as most vendors will try to make money off a tourist.
U.S. dollars are widely accepted in hotels, tourist shops, and for large purchases.