As of March 7, 2011, the U.S. Consulate General in Mumbai, India has indicated that they will no longer offer the services of handling H-1B and L-1 visas. Applicants for H and L visas may now schedule appointments at Chennai, New Delhi, and Hyderabad.
For more information from their website, please go to: http://mumbai.usconsulate.gov/applyingmain.html
Anyone with questions about this change can email the US Consulate General in Mumbai at firstname.lastname@example.org .
As I know from personal experience, many clients go to Mumbai to have their visa stamped and other services. Those that really need an appointment at Mumbai can send them an email to see what the options are and whether any exceptions can be made.