OK so you will need the following
1) Google voice number (see here for how to set up from Canada)
2) an Ipkall number from here
3) a Sipsorcery account here
4) a softphone installed on your iphone, like whistle phone, fring
Total cost = $zero
Then,
1)Register google voice at your ipkall number. You'll need a voip account to do that. There are loads to choose from, you just need a sip account name, password and proxy for a day. Probably you can get a free one say voipcheap that gives you a couple of minutes free trial. You need to forward your ipkall number to your voip account so you can answer it. Google calls you and you have to dial the two numbers they show you on the screen. After that you don't need voip account and google will think ipkall is your home number.
2)Forward ipkall to your sipsorcery account, username, proxy is sip1.sipsorcery.com
3)Register your softphone to sipsorcery account
4)put this dial plan in sipsorcery, numver 10, simple plan. Change the bits they tell you to change.
5) Now you can call from your softphone to the whole of north america for free, civilization at last...
