The Central Bank Survey of Foreign Exchange Market Activity is compiled and posted on the Internet by the Bank for International Settlements (www.bis.org/publ/r_fx96.htm).
To invest in foreign currencies, you can set up an online brokerage account at sites such as Forex Capital Markets, Forex.com and Oanda FXTrade, and others. You could also open a foreign bank account (at Everbank.com or elsewhere), or you could invest in a mutual fund the holds foreign bonds and doesn't hedge currency fluctuations.