I looked at various shipping options to get a bike from Canada to Portland earlier this year, and as soon as you shipped across the boarder, the cost rose to the stratosphere -- I ended up taking the bike on the Air Canada plane with me, and it arrived safely. $50 for the bike, and $25 for the checked luggage.

So if you're starting in Seattle, a shipping company might work, but probably not if you want to ship to Vancouver or Victoria.