Currency Converter - Yahoo! Finance
Currency converter related to foreign exchange. Includes euro, yen, dollar, british pound, swiss franc and more.
http://finance.yahoo.com/currency?u

Go Currency
Money conversion service to convert your money into another currency in an affordable and simple way.
http://www.gocurrency.com/

Oanda.com - FXConverter
Multi-lingual currency converter with up to date exchange rates provided from leading market data contributors and is filtered for validity. Exchange rates for 164 currencies.
http://www.oanda.com/convert/classic

XE.com - Universal Currency Converter
You can perform interactive foreign exchange (FX, or forex) rate calculations, using live, up-to-the-minute currency rates.
http://www.xe.com/ucc/