I've started compiling Forex Futures data to determine currency volume.  It's still in the works but you can click on the link to the right, Forex Volume to obtain relevent data.  I'm preparing to graph open interest, long, and short positions for the last 5 years for each Currency.  Also read the post from Friday regarding Foreign Exchange Volume to understand how to interepret the numbers.  I'll have a full explanation once I'm finished crunching data.