Number one is climate change--the evidence convinces me that "AGW"--Anthropogenic Global Warming--is the most significant challenge of our time.
Failure to address it--and I suppose I should say, "continued failure to address it"--will be disastrous for humankind, resulting in a great many premature deaths and immense financial, ecological, and cultural loss. My involvement in Hubpages is motivated primarily by a desire to educate the public about the science supporting this (admittedly gloomy) view of things.
That said, I also enjoy documenting other aspects of life which I happen to know something about, so I have what I call the "How (not) to. . ." series--this series deals with miscellaneous skills (either useful or amusing) such as carpentry, plumbing, and puzzle-solving.
I write occasional "meditations" as well, and I expect to write some about music, which is the area for which I am actually trained.
As to my country, I am a Canadian citizen, but I live and work in the Atlanta, Georgia area. (I suppose that gives me some perspective on climate change right there!)