There are a number of other organisations and individuals working on this issue,  including:
Save the Powerhouse , an Ultimo-based state-wide  community campaign (Facebook page)
North Parramatta Residents Action Group, advocating for saving Willow Grove historic house, and the conservation of the Fleet Street  heritage precinct and opportunities for cultural uses (Facebook page)
Mr Tom Lockley: Pyrmont History Group, Powerhouse Museum Interest Group

MPs: members of Inquiry into Museums & Galleries, NSW Govt:
Robert Borsak robert.borsak@parliament.nsw.gov.au
David Shoebridge David.Shoebridge@parliament.nsw.gov.au
Walt Secord walt.secord@parliament.nsw.gov.au
Rose Jackson contactrose@parliament.nsw.gov.au
Inquiry office gpscno4@parliament.nsw.gov.au

MP Jamie Parker      and  MP Alex Greenwich

Links to more information:
Powerhouse Museum / Museum of Applied Arts and Sciences 
National Trust of Australia (NSW), supporting retention of the Powerhouse Museum in Ultimo and development of a satellite museum in Parramatta   
Council of Australasian Museum directors has a useful summary of museum news