http://calgary.kijiji.ca/
I have been looking for a while myself and I have found that this site (which is run by eBay I believe) to be suprisingly good.
Trader is always a good bet too.
On a side note, if you are looking to have a car inspected I went to a place called Custom Car Clinic in the SW and dealt with a guy name Rob something. He was fantastic, seemed very honest and helpful, squeezed me in on short notice. I will most likely have all my work done there from now one.