If you have friends or family abroad, some hotels will have rooms booked out to other guests who many not be affected. It really depends, some other countries are not effected. Europe and UK worse off or course.
The hotels all have their own T&C's and some will be more considerate and offer a reduce rate to help out and some will rip you off. Negotiate.
This following information is for people who have booked a holiday and are in the hotel and now can't get home as their return flight's cancelled. This is hot of the press.
I have had some news (I hope) for those stuck abroad. If you are stuck in the hotel you originally booked into before the disruption, now some airline's are paying for the extra accommodation costs including meals and one three minute phone all (excludes taking advantage like alcoholic drinks etc). This is because of the intensity of the problem with the volcano still erupting and ash still flowing across UK controlled airspace will remain in place until at least 0100 (UK time) tomorrow, Sunday 18 April.
If you are still in the resort/that you checked into before the disruption, and can't get home, passengers should contact their airline, tour operator or agent directly before checking out of the hotel and going to the airport. Some advice is don't go to the airport if your flight is cancelled as the airline can not assist you at the airport. Pointless.
If the hotel require you to pay (and do not accept that the airline will cover costs) use your credit card to make any additional costs in the hotel, and keep the receipts, to get a refund from the airline, insurance company or credit card company.