Question: What is the most reliable and up-to-date source for getting world currency exchange rates?

Answer: 
I consider [Reuters](http://www.reuters.com/finance/currencies) to be THE source.
[XE](http://www.xe.com/) and [Oanda](http://www.oanda.com/) would be one of your safe bets. And it is in real time too. But a strict no no for using their services. They give very low exchange rates.