Actually, MaRS has been not at all useful in my experience. Additionally, Toronto is home to a lot of great startups, though many are a bit smaller than the giants, but some are giants. Shopify and 500px are good examples. Smaller examples are AgileBits who make 1password and PagerDuty. There are more too, in enterprise, legal, you won't have heard of these as the aren't consumer facing.
MaRS seems to be much bigger in science and medical startups, and unless you look for what they've been supporting it's like you mentioned most won't have heard of them because they aren't consumer facing.
I think I mentioned elsewhere -- Shopify and 500px (I've applied there and failed lol) are some of the unicorns here. Good companies with good products and good talent. I'll have to check out AgileBits.
I work for a company that sometimes deals with other smaller startups but they can be fleeting in lifespan.
I would love to find something viable to join in on vs. the enterprise environment I find myself in now. Though I honestly haven't had my ear to the ground as much lately.
