Howdy fellow Canucks!
I use paddockwood for ingredients I can't source locally. Their prices are very competitive and if I use Xpress-post for shipping I often get things within 2-3 days (gotta love Canada Post).
There is definitely not as much available online in Canada. When I started acquiring my kegging supplies I had a difficult time finding what I needed. Paddockwood does have a bunch of stuff but it's kind of pricey. I use kegworks.com for that stuff now. They do Canadian orders in Canadian dollars and use some service that includes customs fees in your shipping charges (borderfree or borderless or something, I can't remember).
I've ordered the odd item from Austin Homebrew Supply just because it's so popular. They really do have a great selection and the prices are good but they only ship to Canada with UPS and they KILL you with brokerage fees. I ordered an aeration kit for 31USD and UPS billed me 23CDN in brokerage. Ouch.