Up until recently I used callserve for my Canada to UK calls but Skype has the edge so I'm a convert.
For the computer challenge friends in the UK I have cut their calling costs to me using X-lite free world instead of them having to pay up to 15 UK pence a minute for a call to Canada they call a 0845 # and dial my user # and call into the pc for as low as 1 UK penny a minute. I have also set up a 0870 # at a slightly hight rate 1.5p that just calls me direct without the dialing of the user number. One program to do it all a true VOIP-PSTN WOULD BE AMAZING, and see off the competition. Just a though.
Have a great day
Martin