Google’s OneBox for currency conversion until recently, when searched for [1 usd in eur] or [200 gbp to peso], displayed the result only. Now, the new updated OneBox includes a graph for historical exchange rates and an interactive tool that lets you select a different currency from a long list or change the value you want to covert and instantly get the result.
A similar tool is available at Google Finance, but it's more convenient to access it from Google Search and you don't need to search for USDEUR to convert US dollars to euros.
For some reason, when you search for [currency converter] from the US, Google tries to be helpful and shows that 1 US dollar = 0.6957 euros.
[Thanks, Aahan, Alex]