Sydney, being the bustling and multi-cultural city that it is, houses a plethora of foreign consulates. Most are located in the downtown Sydney area, and most should be contacted by phone before walking in.
Consulates are governmental bodies that are able to assist members of that country with certain passport or visa issues, as well as provide citizen services. They are also there to assist interested parties from other countries with their visa inquiries. Each consulate is different, so do be sure to consult the official websites for details on what they can specifically assist you with at that location.
Consulates for English-speaking countries in Sydney: