The first thing to note is that most providers in Canada require you to have a Canadian street address and a credit card. The staff in the cellphone shops are trained (or simply don't know any better?) that monthly contracts are the only option. Do not be dissuaded.
For only minimal (unverified) details of name and (any) date of birth, Fido offer a prepaid SIM (both full size and micro for iPhone/iPad) for free with top-ups from CA$10. This comes with a pretty ordinary tariff of domestic calls at 30c per minute and domestic texts at 10c each.
However, what I was after was data and this proved to be the real bargain. CA$2 buys 20MB or 24 hours, whichever comes first, and CA$7 buys 125MB or 7 days on the same terms. As soon as you attempt to use data or exceed your purchase allowance, you'll receive a text from 3330 offering you a link where you can buy the data add-ons. The fee is taken from your airtime balance.Top-ups are readily available from tabacs where you'll be provided with a till receipt showing a fourteen digit number; dial *868 and follow the (tortuously slow) prompts and then wait for the confirmation - you'll get a confirmation text from 9000. You can check you available balance by dialling *225.
Fido's website says there's also a CA$25 500MB "month" option, although I didn't see this. Generally, the 3G service on my iPhone4 was very good, with some coverage even available on the underground Metro. To give them their full name, Fido Solutions are part of Rogers Communications and share some tower infrastructure in some locations as well as their own gear so I suspect coverage is just about the best that's available. That said, I didn't venture beyond the city so beware before you choose to rely on data for navigation, safety etc.
