I haven't heard of a prepaid international data plan from anyone in the US. AT&T has a fairly expensive international roaming data plan. Once you are over, you can buy prepaid phonecard SIMs from vendors in each country, but there are very few that will let you use them internationally over all of Europe and the Middle East and data tends not to be high-speed.
The one carrier that I can think of that covers most of the countries that you mentioned is Vodafone. Vodafone has a roaming prepaid card that offers WAP data access if you get their "Prepaid Extras" pack. It will work in Spain, Israel and Egypt, and Belgium, but not - to the best of my knowledge - in Holland. Googling for this, I didn't find a good link... but when I was last in Europe (about 9 months ago) I remember hearing about it. I think they offer UMTS on prepaid as well... but I'm not sure of this. I did some Googling, but I couldn't find many details - you may have more luck.