With the chaos that the eruption of Eyjafjallajökull has caused to the airline industry, people are forced to return to land and ocean travel. Even though most of the large scheduled ocean liners have vanished, there are still some great options!
It is possible to book a cabin on a freighter. It takes a bit longer, and is actually more expensive than flying, but at least it will get you to Europe. Check out Freighter travel on Wiki Travel for some information on options.
Since the airport in Reykjavik is still open, you could fly there with Iceland Air, take a tour to the now famous volcano while you are in nearby anyway, and then continue by ferry from Iceland to Denmark on the Norrøna.
Or, if you have cash to spare, you can board the luxurious Cunard Queen Mary 2 for a Trans-Atlantic trip of a lifetime! There are some cheaper alternative Trans Atlantic cruises too. Guaranteed to be more memorable than an 8 hour flight in Economy class (or a 5-day camp-out at an airport).