I am going to need to call Canada while travelling in Paris and London, Belgium, etc. What is the best and cheapest way to do this. Pre paid phone card?
Locally-purchased calling cards are usually the way to go to give you the cheapest rate. In some countries, there are a couple of different kinds...make sure you get the one for international calls...it's a cheaper rate. Check out the per-call connection charges to make sure you're not nailed that way. Cards are available in tobacco shops or at newsagents.
If you are taking a laptop, just load Skype on it before you leave. It is free to load and calls would be about 2cents per minute from Europe to a land line and a little higher to a cell phone. You can prepay $10 and that will last a godd while at those rates. Otherwise a card purchased in Europe is the cheapest way to go.
I've had good luck buying pin cards from tobacco/news stands. I buy a card that works in one country, use it, then pick up a new card in the next country.
Short of taking a laptop and loading Skype, there are more "call shops" popping up or internet cafes offering VOIP (Internet) calling, usually at a rate rivaling calling cards.