In terms of service providers, there are 2 coast-to-coast GSM providers (actually only one holding company with two different brands): Fido and Rogers. The other two coast-to-coast providers (plus their alternate discount brands, and the virtual operators who leech off them) are non-GSM; however, they are apparently preparing to phase in a shared GSM network in the Vancouver area, in time for the Olympics.
As far as data options go, they both have smartphone-compatible data add-ons available for postpaid customers, starting at $25 per month for 500 MB of data.
However, judging by Fido's website, it doesn't look like they offer any data add-ons for prepaid customers - just the pay-per-use rate.
Roger's website lists a $7 unlimited mobile Internet add-on for their prepaid customers, but it is only meant to work with lightweight WAP browsers, not for general-purpose data such as HTTP web browsers. It's not certified to work with smartphones, PDAs, or laptops at all. So for the iPhone, the only option available would also be the pay-per-use rate.
