Hi,
Depends on how far you are willing to travel to camp. Within 200km of mumbai you will get many options. Near(80km) to mumbai you may find good locations towards madh, vasai, panvel, karjat, nashik highway Letscampout can help you organize near Mumbai Happy camping
Few camping otions can be:
Bhandardara camping
Velas
Vaitarna Lake
Rajmachi Fort
Malshej ghat
Igatpuri cliff camping There are many organizers available these days, for above mentioned options.