Links are for information not endorsement.
A ABC website: Sydney Sidetracks | ABC Open (beta); ABC Open Camera Club; Now and Then (photography project): Series 1 | Archives Outside (New South Wales archival collections) | Australian Dictionary of Biography Online | Australian Geographic; AG Blog (This Day in History) | Australian Government: National Measurement Institute | Australian Museum | Australian War Memorial; blog
B Blue Mountains Association of Cultural Heritage Organisations | Blue Mountains Historical Society (Wentworth Falls) | Blue Mountains Library – Local Studies’ photostream (Flickr) | Blue Mountains Local Studies (Blue Mountains City Library, Local Studies Librarian, blog) | Britannica: blog
M Mid Mountains Historical Society (Bullaburra, Lawson, Hazelbrook, Woodford, Linden) | Milparinka Heritage and Tourism Association: Corner Country, Outback NSW [north of Broken Hill] | Monument Australia | Mosman Library: Mosman Memories; blog | Mudgee District Historical Society, Colonial Inn Museum | Mudgee District Local History
N National Archives of Australia | National Library of Australia: Trove; Australian Newspapers; National Library eBooks (free downloads); Picture Australia | Nepean District Historical Society (Arms of Australia Inn Museum, Emu Plains) | New South Wales Government: Land and Property Management Authority | NSW Law Almanacs
S Scenic Hills Association (Campbelltown area, Sydney) | Scratching Sydney’s Surface (blog) | Society of Australian Genealogists | Springwood Historical Society | State Library of New South Wales | State Records Authority of New South Wales | State Records Office of Western Australia | Strathfield History (Strathfield District Historical Society)
U Unlock the Past (resources for history and genealogy)