It took some doing, but the iPhone 4 has been unlocked. Unfortunately, you can't get your hands on what you'll need to do it yourself just yet.
A member of the iPhone Dev Team who goes by PlanetBeing has posted a picture of an iPhone 4 on Canada's Bell network. The feat was made more difficult with the iPhone 4 because iOS 4 on AT&T needed a soup-to-nuts rewrite of ultrasn0w.
We don't have a timeline for when the updated ultrasn0w and Spirit will be released, so we'll keep our ears pressed to the ground on that one.
For now, at least one iPhone 4 is flying free in Canada! Spread your wings, little iPhone, and keep those Canadians away from your lower left-hand corner.