XE.COM gives conversion rates but the credit card companies do charge a conversion fee so beware if you have a non-U.S. credit card. You will be charged a premium on your U.S. dollars. If you are doing a lot of booking or buy from a lot of U.S. sites, it might be worthwhile to see about getting a U.S. dollar credit card. I understand BMO has one although I haven't checked it out yet.
