I found this answer from yahoo ;)
Concrete is usually bought by the cubic yard. Here in MS I cost about $90 per cubic yard. There are 27 cubic feet in 1 cubic yard, so, it costs $3.33 per cubic foot. How much per SQUARE foot would depend on how thick it was... Sidewalks and Paving are usually poured at around 4" thick(1/3 ft) so...
@ 4" thick concrete would cost about $1.11 per square foot. This does not include labor to prepare and pour the concrete.
I wouldn't think the price would be much different in Canada. :)