Chile's currency is the Chilean peso (CLP). Other currencies are not widely accepted, but most cities have exchange bureaux with resonable rates on euros and US dollars. The rates should be published on widely visible boards.
It's not advisable to exchange currency in the hotel or the airport as the rates are awful. Just be patient.
Never exchange money on the streets, specially if a "helper" indicates you to follow them.
The automatic teller machine (ATM) network in Chile is respectable in coverage--they're all connected to the same service and enable standard transactions.
Credit and debit cards are widely accepted in most of the independent commerce of major cities and in all chain stores, no matter where they are. The pinpass security system has been introduced for credit cards, so you will only need your personal pinpass four digit code as it exists in other parts of the world.
In late November 2010 €1 ≡ CLP 639, £1UK ≡ CLP 752, and $US 1 ≡ CLP 483.