Foreign Currency Exchange, or ForEx, is the most liquid and volatile market in the world.
Many CFD and market providers will allow you to trade currencies as a part of their package or trading platform. You can also find specialized brokers who will allow only ForEx trading.
The benchmark rates can be seen on Bloomberg.
Current official cash rates are available in the box on the right-hand side. To see more data on Australian Dollar, see Australian Currency page. US Dollar rate available at Federal Reserve Board web site (link). Historical rates available at fxstreet.
A good explanation on how currency pairs are traded is available at Oanda.
To see current Euribor rates - click here.