Is it fairly hassle-free to drive between countries in Europe? Do you have to go through customs or anything, or is there just a checkpoint on the highway and you hand them your passport?

No, since +/- 10 years all the borders were lifted. Bye-bye customs. (not a good evolution IMHO)
So as long as you stay in the western European countries (with exception of Switserland, a few scandinavian countries and England) you won't ever be stopped at the border.
In some countries (like France), you'll have to pay for driving on the highway. In most countries it's free though. Oh, and keep in mind that fuel is A LOT more expensive over here!

Also, LTJBukem is correct. Since jan 1st of this year (almost) all EC countries have the same currency. We're all still getting used to it.

Oh, and Rob, french fries are not the Dutch's national dish! Croquets are! French fries are a Belgian speciality dammit !

I wish I could be there at this meeting, but the middle may or june would be very bad for me as this is the middle of my final exams. I sure hope there will be a meeting in july or something in the future!