Originally Posted by FLYDCA
Not a single US based pre-paid GSM provider allows International roaming that I know of. You can however buy pre-paid sims before your trip at this web site:
http://www.telestial.com
Prepaid SIMS are terribly easy to find in Europe and some will let you roam here. As Dino2020 pointed out, the prices charged by this web site are in my opinion, bordering on obscene. Check out the web sites for companies like Virgin Mobile, Vodafone and Orange to see how cheap these cards are if you buy them in the country you are travelling to.