Closest thing to free is Magicjack. The hardware costs less than Can$40 and you can make free calls to any phone in Canada or the US for a year. After that it's $20/year unless you buy 5 years for $60 (a dollar a month).
I've used one for a few months and it's already paid for itself many times over. It works great with lots of volume and faithful sound. In fact it sounds closer to a regular landline than any cellphone.
If I only needed to call the US or Canada MJ would be ideal but I need to be able to call other countrys, such as Thailand and The Philippines, from South Korea. Skype works fine for this and at 2 cents a minute the cost over a years time is actually less than MJ. Yahoo has a similar service to Skype though I've never tried it.