So I stumbled across this handy tip on MacOSXHints.com describing how you can use the Stocks Widget to give you the current exchange rates between for example the Euro and the Dollar. The cool thing is that this widget comes with Leopard, Tiger and best of all the iPhone, which means that this hack works even when you are on the road!

Just add codes like these below to your widget and they will be recognized:

GBPUSD=X (for £UK to $USD rate)
GBPEUR=X (for £UK to €EUR rate)
EURUSD=X (for €EURto $USD rate)

This works because the Stock Quote widget uses the Yahoo! Finance site in the backend. Go there for more currency codes.

[More hacks for the Stocks Widget]