As you probably read the volcanic ash coming from Iceland is causing all sorts of cancellations and delays all over Europe. From a travel insurance point of view the main coverage that would apply would be travel delay. This often overlooked coverage kicks in if you are delayed for usually 6-12 hours due to natural disasters or common carrier delays. This coverage will reimburse you for reasonable additional living expenses such as hotel stay and meals due to your delay.
Its also too late to purchase travel insurance to cover this, since its happening now and its foreseeable that it could affect travel in the immediate future.