The market isn't as stupid as it looks at first glance. Most arbitrage opportunities get argitraged away. If you want to look into currency arbitrage, take a look at the Economist Mac PP index below from 16 Janyuary. Sell Iceland and Switzerland and buy Argentina, China, Russia and the Phillipines. Capital controls can keep a currency out of sync for a while, so I wouldn't bet on China. I think the Swiss run a corrupt economy, so they sound like a good bet. I happen to have visited and liked Iceland, so I couldn't bet against those Scandinavian beauties. They also are highly educated, uniformly speak English, and sit on top of some gigantic broadband pipes between Europe and North America.
Sorry, couldn't get the graph to post. It's on the Economist's Web Site, subscriber pages.