You can find exchange rates between foreign and American currency through the U.S. Treasury Department website. The rates depicted on the U.S. Treasury site are not current, but the effective date for rates listed appears at the top of the page.
You can also find exchange rates between foreign and American currency through the Board of Governors of the Federal Reserve System website. The Federal Reserve site lists the exchange rate per U.S. dollar between American currency and the currency of 23 countries, as shown on the site.
An additional resource for finding currency exchange rates is Oanda. Choose "US Dollar" in the field labeled Currency I Have and the foreign currency you wish to convert in the field labeled Currency I Want, as stated on the Oanda website.