I believe the Annex is the most vegan-friendly neighbourhood. In just a few blocks you can find:
Noah's Natural Foods (Bloor & Spadina)
Overpriced for most stuff, but does have a wide selection. Most importantly, it houses a non-overpriced cafe that makes lovely food. You must try the 99 cent chocolate chip cookies!
Taste of Nature (Bloor & Brunswick)
My personal favourite health store. They're super nice and reasonably priced. Very reasonable bulk section.
Health Valley (Bloor & Brunswick)
Home of Merry Hempster Vegan Lip Balm & the cheapest JASON hand soap in the area. Super nice owner.
Juice for Life Restaurant (Bloor & Bathurst )
Fancy enough, but casual too. Very down to earth menu and of course, super juice. Vegan unless it clearly says otherwise.
Kensington Natural Bakery (Bloor & Bathurst)
Not actually in Kensington, but what the hey! This is where I head for my pies, particularly for my pumpkin pie. Soooo good. They also sell day-old bread for 99 cents.
Eternal Abundance (Bloor & Bathurst)
Organic veg store. Often has major sales that make their vegetables cheaper than the regular grocer's! They also sell soy milk and other such products.