This is in response to Tim Bray's post: I'm voting Green. It is rewritten from a comment I left on that post.
Tim sums up my feelings pretty well. We're in Vancouver Centre, which has been Liberal (Hedy Fry) for as long as I've lived in Vancouver. Adriane Carr is our Green candidate, and I think she'd make a great MP.
While I agree that the environment is a key issue, the fact that the Greens oppose the proliferation of war is huge too. Next to the rising threat of nuclear war, even climate change pales in comparison. The difference is that we are 100% certain to have climate change (we're already in it) and it has a large "lag," so the longer we take to act, the worse the outcomes. With nuclear war there is still a chance of avoiding it, and we must avoid nuclear war. The cold war may be over, but the Bulletin of Atomic Scientists has the Doomsday Clock at 5 minutes to midnight. Recent posturing in the US over Iran and South Ossetia make that threat even more likely. I think any party besides Harper's Conservatives would be an improvement, but the Greens most of all.
Finally, while the Conservatives tend to be thought of as the financially sound party, they are the ones who have gotten us in the current mess with deregulation and a lack of oversight. The Greens actually are very fiscally conservative and want to put taxes in the right place, on pollution, rather than on income. A green economy could bloom!
Oh, and I'm a dual citizen, so I will be voting for Obama next month as well.