Chor Bazaar is infamous for being a thieves market, where stolen goods are sold at a cheap price. However, having visited Chor Bazaar recently, I've learned that many items bought and sold at Chor Bazaar are mainly pre-owned and often what would constitute as junk for most people, which is why it's easy to get a good bargain.
The most popular street at Chor Bazaar is Mutton Street; it's lined with dingy, little shops on both sides of the street selling used car/motorbike spare parts, antique clocks, classic 70s and 80s Bollywood posters, bronze statues of Hindu deities, statues of Buddha, old paintings, antiquated cameras, trinkets from around the world (you can find knick-knacks from Holland, France, China and several other countries), old coins; you get the gist.
Chor Bazaar is located in a predominately Muslim area; it's best to dress conservatively when visiting. If you have the time and energy to look and bargain, you can perhaps find something of value, however I suggest going it with no expectations of finding lost treasures, most of the stuff available at Chor Bazaar is junk really! International tourists will probably enjoy a visit to this local market; if not for the trinkets, then maybe for the cultural experience.
The market is closed on Fridays and many shops are briefly shut during namaz (prayer time) in the afternoon on weekdays too. Chor Bazaar is accessible from Grant Road station (east) on the Western line and is about a twenty minutes walk from there. If you're not up for a walk through the crazy streets of chaotic old Mumbai, a taxi ride would be more suitable.