I use www.xe.com to check exchange rates.
Why do you need to worry about exchange rates, just change your default currency in the AdSense control panel to Euros, then every month Google in Ireland will send your cheque made out in Euros, and it will be exactly the same as your earnings in the admin screen.
But in Europe it is often a good idea to also add your Euro bank account details to the AdSense admin area so the payment can be made directly into your account. That way you save on bank processing fees.
When you add your bank account Google will make a small test payment, you check your bank statement, tell Google how much the test payment was and they change your payment to verified. Very easy process.
zika (7 November, 2010)
Also, all eurozone countries should accept direct payments, this is EU law and would put Google and the customer's bank in breach of Eurozone regulations if they don't accept direct payments in Euros within the Eurozone.