Land is the most important commodity in Mumbai, and the source of much of its problems. There are always several development projects going on, usually within the scope of the current masterplan for Mumbai (1996-2011). A major ongoing project is the Bandra-Kurla Commercial Complex.
A few overall numbers about housing and land in Mumbai. Also read about the problem of collapsing buildings.
More than half of the population of Mumbai lives in slums. Read about the history of slums, ponder the Magnitude of the problem, and tune in to the current thinking on slum rehabilitation and improvement.