I wanted to call this to everyone's attention since on my recent trip back from Venice it happened to me. As a result (though it can hardly be called lucky considering the circumstances), I was luckier than almost all other passengers.
While the US has a new passenger bill of rights that has good and bad points (the bad point is that more flights are taxing back from runways before they get slammed with the 3 hour delay cost and cancelling the flight instead, the EU has always had a much more robust Passenger Bill of Rights which affects all flights, no matter the airline or destination that emanates from or is going to Europe.
While the EU is currently debating some changes to it, especially regarding the fines airlines have to pay you, you are expected to arrive at your destination without interruption or you are entitled to accommodations, meal vouchers, transportation between airports, and getting on a different airlines' flight if necessary. This happened to me on my return from Venice. The Delta flight from Venice got in just fine -- early in fact -- but then I landed in JFK where my horrors usually begin. And they did, trying to get the 30 min flight to Boston. I was put on an earlier flight that had been delayed twice because of weather, but still looked like it would make it out before my scheduled 8pm flight. Except that we sat on the runway for over 2 hours, bringing it close to 8pm. The pilots, for a small Delta connection partner, were quite candid saying that while weather in Boston had been an issue all day, there was more to it than that. They said they didn't know if they could get us out because they were running out of flight hours and would soon be grounded. Around 7:30 pm we taxied back to the gate. I went straight to the Skyclub. It would have been impossible to make the 8pm flight by then because I was in Terminal 2 and it left from Terminal 4. (BTW, for those of you who don't know, I hate JFK more than almost any transportation entity I can think of.)
The one and finally two attendants on duty were telling people they'd find lodgings for them at a discount (but which would cost them around $300 a night and result in two trips -- to the hotel and to LGA for the next flight the next day). People were getting really angry. Then the Skyclub woman got to me (as 8pm passed and that flight took off -- so much for the weather delay others were told). I told her I flew from Venice and was entitled to the EU Passenger Bill of Rights. She wrote this down about 3 times, and kept asking me exactly what it was called. She called various supervisors, all the while the crowd behind me getting more and more restive. Finally, she said loud enough for everyone to hear while on the phone "She's a valued customer." I thought I might get murdered in that instant, people were so angry. But it was my Platinum Elite Plus status as well as my knowledge of the EU PBR that got me a free hotel (pretty awful, smelling so much of clorox I thought someone must have been murdered in the room, but apparently the only one in the area because that was the week of all the worse storms, so anything just to sleep 3 hours). They also got me prepaid transportation from JFK to the hotel, a meal voucher (which I could only use the next morning since by then it was 10:30 and there was no hotel restaurant) and prepaid transport to LaGuardia at 3:30am for the 6am flight, where I used my voucher.
The key is it really helps to be elite status, but regardless, and certainly if you're flying to or from Europe, know your rights and demand them. If they deny you you could end up getting far more than I got because all I wanted was a place to collapse.
Hope this helps someone else!