I recently had to attend a class in Copenhagen, Denmark, to get to learn the CMS system we use at the office a little more in detail. I had planned on taking a flight down there on a Wednesday, attending the class Thursday and Friday, then flying back home Friday evening. However, Iceland didn't quite want it to go down like that.

One week before departure the Eyjafjallajökul volcano on Iceland decided to erupt, throwing tons and tons of ash into the atmosphere. The winds favored this ash and placed it right on top of Northern Europe, causing all air traffic to be suspended.
The following Monday all flights were still canceled and I couldn't risk waiting any longer, so I got a refund from the airline and ordered a ticket on the Oslo - Copenhagen ferry instead.
That meant that I would have to leave on Tuesday instead of a Wednesday, and I wouldn't get back home until Sunday afternoon. Gone for almost a week for only a two day class. The next day airports started to open again, but then it was too late. I would have to take the ferry.
The trip was actually still quite a good one, though. I got to stay an extra night in Copenhagen, saw some of the nice surroundings (as the ones of you who follow me on Twitter have already seen). I had some good food, and made some new acquaintances, and most importantly, I passed the exam at the end of the class with flying colors (95%! woot!) so I'm now a certified Sitecore .Net Developer!
There was one positive side to the volcanic ash in the skies, though... it showed off it's true colors in some amazing sunsets, one of which I managed to capture on the ferry ride from Oslo to Copenhagen.