What is the most reliable and up-to-date source for getting world currency exchange rates?
I consider Reuters to be THE source.
Here's one that appears to be real time.
If you're wanting to trade, you'll likely get something better than this with your forex trading account.
Forex rates are universal. Most of the website provide you with almost the same exchange rates with a margin of +/- 5 pips which is usually due to different spreads provided by different institutions or server delay.
www.netdania.com www.xe.com www.fxstreet.com www.dailyfx.com
I personally use netdania's application on my iPhone