Alright. Maybe not your mother's cute organic market. There's definitely a wee bit of grit here that's not for everyone. As someone who's done their fair share of market work, this place certainly weeds out the weak quickly.
The top has a mix of different fruit/veggie vendors (most of which appear to be truck farmers/non-producers), some cheese places, lots of different meats and seafood and some great little bakery type places in the mix. The best in my opinion is the bagel place in the back left corner. Montreal bagels!!! Weeee! Down below is more crafty/arty land, but there's also a place with lots of dried foods and goodies. Beware though. I've seen many a kid launch a hand in to the open bins only to fondle the dried apples or candies within.
Great to stop by on a late Sunday or Saturday morning and grab some bagels, fruit and other snacks for breakfast and then wander over to the sculpture garden or a nearby park and lazily start your day.
Producer/non-producer withstanding, the St Lawrence Market is a must if you're visiting Toronto. Just don't fool yourself into thinking its a farmer's market. Let me tell you it ain't.