It's actually quite simple,
1. the iPad is only available for sale in the US. iTunes' US store is the only store CURRENTLY selling all iPad apps. Once the iPad becomes available in Canada (or the UK, Germany, etc) the Canadian iTunes store will begin selling iPad specific apps. This means that being based in Canada, and while you've managed to get an iPad, you can only shop in the Canadian iTunes store.
2. Persons are only able to make purchases in the iTunes store of the country they have a bank account debit/credit card in. You can create a US account as stated previously, but will have to rely on gift cards to purchase iPad specific apps UNTIL the iPad becomes available in your country ( late April, supposedly). Afterwards, all iPad apps will be available in your own country's store. (unless you have a US creditcard or bank account)
3. There are several types of apps currently in the iTunes store: A. iPhone/iPod touch only apps, B. Apps made for iPhone/iPod that have been updated to include an iPad revised edition, C. Apps designed for, and exclusively sold for iPad.
Apps appearing in foreign iTunes stores now, in countries where the iPad is still not available ( rest of planet) are most likely the apps that were made for iPhone/iPod and have been updated to include both versions in one program. For this reason you might see them appearing in iTunes stores outside the US (though that's not 100% certainty). I doubt apps are appearing in foreign iTunes stores that were made exclusively for iPad and are seperate purchases.
So to answer your question, you WILL BE able to purchase apps for iPad on teh Canadian store soon, but most likely not until iPad has it's official release in Canada. You can however create a US iTunes account with 'none' as the payment option, get US gift cards, and then purchase apps off your US iTunes account until Canada's release date. Or.... You can just wait till it's officially released in Canada (which I doubt you Want do ;-)