This chart is a bit of fun, but actually contains some useful information. The index, started in 1986 by the Economist charts the price of a Big Mac in US dollars across the world, It is an easy way to compare the value of foreign currencies against the dollar:
Switzerland has the most expensive Big Mac at $8.17. The least expensive is Taiwan at $2.39. Makes you want to live in Taiwan, yes? A rough measure to be sure, but the local price divided by the US baseline gives an approximation of the implied foreign currency exchange rate. Compare this to the official rate and you get the amount a currency is under or over valued, As US people at the games are finding out, Europe is pricy (3.17% overvalued measured against the dollar)