Traveler's checks seem to have fallen out of vogue; most places in Europe charged a big fee to convert them to cash last time I visited.
The best deal the last time I went was either withdrawing cash using your debit card at an ATM and paying the fee or using your debit or credit card directly (if allowed), but you need to determine the fees ahead of time and see if they make sense. Call your bank to find out what fees they require for this. At one point, there was no additional fee, though I doubt this is still the case. Sometimes it even is better to buy the foreign currency in the States ahead of time (though, obviously it's not very safe to carry all your currency).
Here are some more tips:
http://www.ricksteves.com/plan/tips/money-travel-tips.htm