There's something called the Big Mac index. What does a Big Mac cost in the country of choice? Of course this is misleading, as in some countries you have to pay extra for each packet of ketchup (Germany), and in some there are no Big Macs (India).

I like the index Frommer's does, where they tell you what it costs for a local beer, a movie ticket, and a bus or subway ride, as well as hotel and meal costs.