I visited Dhobi Ghat near Mahalaxmi train station when I was in Mumbi a few weeks ago. Many folks mentioned about this place as a must-see, becuase of those "disturbing" scenes to mind and stomach, as well as the famous title as world's largest outdoor laundry.
From above the cross-bridge, rows of open-air concrete wash pens bump to sights, each fitted with its own flogging stone, and a male worker standing in the soap water flapping all things to wash, for hours.
However, only if you walk into the ghat, you see what appears to be very chaotic, is actually very systematic, with sections for different purposes (different customers of different requirements), workers (mostly male, and some female for less labor intensive tasks) working on different jobs, processes that connect from one action to another, and new and old tools and machines to help accelerate productivity.
Dhobi Ghat is a very popular attraction among foreign tourists.
By the way, please don't waste time and try to get in from the southeast entry. Some bad guys stand there to bully foreigners and charge unreasonalbe entrance fee (500), which does not exist, and they do not even provide guide service. Try to walk to the northern end of the ghat. There are a few nicer guys that can take you in and guide you throughout, for only 100 rupees.