I'm using Yahoo Finance API like this:
http://download.finance.yahoo.com/d/quotes.csv?s=GBPEUR=X&f=l1
That gives me the current rates for GBP -> Euro.
But how would I get it to list all available currencies?
http://download.finance.yahoo.com/d/quotes.csv?s=X&f=n0 and http://download.finance.yahoo.com/d/quotes.csv?s=X&f=c4` is a start, but I can't get further than that.
Documentation: http://code.google.com/p/yahoo-finance-managed/wiki/csvQuotesDownload
you want to check this out, it is exactly what you are looking for: http://finance.yahoo.com/webservice/v1/symbols/allcurrencies/quote?format=json