Ha, that map looks interesting (the one Anjeza posted). That map shows how the wind blows and thus where the particles accumulate. I don't think any flights are of good idea, because these ash particles do not stay at a same height (they are slowly, but surely going down and eventually gonna be deposited). So that means it is not a good idea even for small planes to fly. :| This is now going to impact the economy severely, especially the airlines.
@94ayd, Yes the ships and land transport are alternatives. But think of the economy of what will this cause and also think of the time needed to go from one place to another. I'm not saying this for tourists, but for other things. Tourists can find a way home (if they live somewhere in Europe), or they will have to wait in the airport, which I know how it is and it sucks big time. :|