While we did do some shopping in Mumbai and Goa, Kolkata was my personal favorite. Probably because a) I'm pretty fluent in Bengali so the communication barrier wasn't too bad b) my parents are familiar with the markets so they were the perfect navigators (most of the time) c) I'm just partial to Kolkata in general since I have roots there.
The street markets were something I cherished as there's nothing I've been to in the US that's comparable. You can find practically everything there. From saris, electronics, fresh produce, school supplies, you name it-- you can probably find it. The fruit sold are soo fresh and unbelievably sweet. They had the best mangoes I've ever had. It's a struggle to eat mangoes in the US now because they're not even half as tasty!
Gariahat: I don't understand how this place only has 3 reviews on trip advisor cause this market is huge! My parents did the majority of our grocery shopping here, as it was very close to our flat, buying tons of fresh fruits and fish daily. Let me just say, the stereotype that Bengalis loooove fish (or maach) is very much true. But if you're brave enough to wander into the fish market, hats off to you for tolerating such an abhorrent scent. Aside from food you can find everything else I mentioned up above-- clothes, electronics, etc.
If you don't plan on leaving empty handed, I would recommend knowing what book you want beforehand. It isn't really a place to leisurely browse. If you're looking for something akin to a trip to your local Barnes and Noble, you should visit the iconic Oxford Bookstore on Park Street, which has been around since 1919.
As you can see, I have so many pictures just from two of the markets. And this is after cutting some out. So I decided to keep the rest for a second post. Until then!