Google rationalized the One Box for currency conversion. Until recently, when you searched for [1 usd in eur] or [200 gbp to peso], Google displayed the consequence and that was it. The new OneBox includes a graph for historical switch rates and an interactive tool that lets you select a different currency from a long list or modify the value you want to covert and instantly get the result.
A similar tool is obtainable at Google Finance, but it's more suitable to access it from Google Search and you don't need to search for USDEUR to convert US dollars to euros. For some motive, when you search for [currency converter] from the US, Google tries to be helpful and shows that 1 US dollar = 0.6957 euros.