This is so open-ended. This really depends on a couple of things - budget and style. There is a wide range of options between paying $400 and $15,000 for a couch.
If you are a fan of leather and don't want to pay too much, costco.ca has a huge selection, they deliver for free, and, more importantly, pick up for free, if you don't like it. If you want to go higher end than that, Bondars has a good selection and caters to a variety of styles from traditional to modern. If you are spending a LOT of money, I would seriously consider bringing in an interior designer (get some recommendations first, because every second hausfrau is an "interior designer").