Some are groups with members & meetings, others are information sites, sometimes with regular emails, or YouTube channels which you can subscribe to free of charge.
Many have their own extensive searchable archives
The Thames and Docklands History Group. (Meetings at Docklands Museum)
GLIAS. – Greater London Industrial Archeology Society. – (Meetings at Smithfield)
East London History Society – Collections (East London , Meetings in Mile End )
The London Topographical Society – (History and Mapping the City).
IslandHistory.wordpress.com – History of The Isle of Dogs
Spitalfields Life – The Gentle Author – (Huge Archive and Daily Blog)
A London Inheritance – (A Personal Perspective with Photos)
IanVisits – (Amazing Daily Pages)
Look Up London – (Guided Tours and Walks)
London Remembers – (London’s Memorials of all kinds)
Layers Of London – (Maps)
Joolz Guides – (Quirky Video Guides, Tours and Books)
National Library of Scotland – (Access to a Vast Map Collection)
EnglishHeritage – (Blue Plaques, Historic Buildings)
The River Thames Society – ( Preserving and Documenting The River and Environs)
London Screen Archives – (Access to Films about London)
Municipal Dreams – (A History of Social Housing Blog)
John Rogers – (YouTube Channel, London Walks)
Geoff Marshall – (YouTube Channel, Travels on London Transport)
Tower Hamlets Archives – (Bancroft Road, Mile End)
The London Archives – (Northampton Road EC1)