Vegetarian Haven, Baldwin St just off McCaul, borderline Grange/Chinatown: This place is just wonderful. The food is mostly Pan-Asian-inspired, with all manner of tofu, TVP, seitan, and tempeh dishes. Everything is really fresh and well-prepared. They also have a wide variety of vegan pastries, cookies, cakes, and pies. In nicer weather than I experienced up there (it rained a lot), there is a patio in front for soaking up the atmosphere of Baldwin Street while feasting. Service is very fast and very friendly.
Fresh by Juice For Life, two locations--Bloor St West (Annex) and Queen St West: Juice For Life is a Toronto chain of juice bars. They've opened two vegetarian restaurants which I can't recommend highly enough. I ate there several times, and everything from juices and smoothies to tofu scramble to veggie burger w/sweet potato fries to chickpea stew and kale in coconut curry over brown basmati rice were delicious. Fresh isn't cheap, but it is good for a treat and the smoothies and juices won't break the budget.
Moon Bean Coffee, Saint Andrew St in Kensington Market: They offer a good choice of vegan cakes and cookies (I especially recommend the chocolate cake and banana bread), vegan soups, granola w/soya or rice milk, and other light meals,snacks, and breakfast items. They have many organic and fair-trade coffees, teas, and herbal teas (I can personally vouch for the vanilla green, assam, lapsang souchong, and ginger-rooibos-calendula teas). Fun, progressive atmosphere. Patios front and back (the back patio is perfect for decompressing after the crowds of the Market).
Bo De Duyen 254 Spadina Ave (about two blocks south of Dundas), Chinatown, 2nd Floor: all-vegan Chinese and Vietnamese restaurant. IIRC, nothing on the menu is more than $8 CDN, with most appetizers and mains in the $5 to $6 range. My mock goose appetizer was massive and delicious, if not necessarily healthy: an entire platter of golden deep-fried soya crepe stuffed with tofu, seitan, mushrooms, and various veggies covered in vegan "oyster" sauce. Good noodle soups, too. This one was an obvious favourite of the local subcultural set--I counted no less than three velvet gowns and four mohawks when I ate there. The place is quite large. No atmosphere to speak of (pink and green formica rules here), but good views of Spadina Ave and the prices can't be beat.
I'm head-over-heels in love with Toronto and am planning another trip later this summer, so I'd be happy to hear of any other recommendations. Of course, to get conversation going in this community, I'd be happy to hear about veggie-friendly restaurants in any locale.