In the United States, we spell canceled with one l (or at least I grew up learning and using canceled with one l).
However, now I see more and more people especially in blogs using cancelled, and have also noticed that on the TV I watch cancelled is the preferred spelling. And a few of my few colleagues (mostly around my age, or a few years younger) kind of informed me that one l is incorrect.
I now wonder: are different forms of cancelled taught in different regions of the country? Or has it become trendy for the younger generation to use the British form of spelling?