Actually... if you just type in an x amouint of dollars to donate, like 100 US$ (for easy maths)
You will be taken to a paypal page where you're required to log in.
Then you will go to a screen showing you your transaction. If you have your currency set as Euro's (I have since it's linked to my dutch bank account), it will show you the exchange rate, how much you're donating in dollars and how much you're actually paying in Euro's.
Now since the rate is ~1.40 dollars for a Euro, you only pay ~80 euro's (to lazy to work out the specific number).
So if you like acting ignorant like me, you go like... OH SHI- 100 dollars is soooo much!!!
Then you see the transaction and it's like... ah only 80 Euro's... that's not that bad after all... xP