More coming soon, but until then here's a good start.
Historical interests:
-SparkleTack :Great blog and podcast on our unique city by the bay.
-OLDSF : Plethora of pictures from long ago.
-Sepia Town :Not only San Francisco, but many many old images.
-San Francisco Museum and Historical Society
-San Francisco History Association
-What's on the 6th Floor : SFPL's History Center/Book Arts and Special Collections Blog
-San Francisco Public Library History Center
-FoundSF :Shared history of our city.
-Western Neighborhoods Project (Outsidelands) : History of the western half of the city, often times having walking tours.
-California Historical Society : Large collection on San Francisco
-San Francisco Maritime National Park : Living history, museum, ships...
-The Virtual Museum of the City of San Francisco
-Using San Francisco History 
-Whatwasthere : images now and then
-Atlas Obscura
-Map of the buildings of the Sutro Baths
 

Walking tours:
-Roamlocal - walking tours with one of the most entertaining and brilliant tour guides.
-SF City Guides - many different walking tours that happen all the time.  Many different areas of the city and many victorian related.   Free.
-Emperor Norton's Fantastic San Francisco Time Machine
-Chinatown Alleyway Tours
-Dashiell Hammett Noir City Tour
-Victorian Home Walk

Socially Awesome (not necessarily steampunk, but worth a gander)
-Tin Can Singing Telegram
-Alien Corset (silkscreen posters by David O'Daniel)
-SF0.org  (games played in the world)
-Timeless Tailor, amazing creator of garments.

Non San Francisco steampunk groups:(this is no where near a complete list)
The Steampunk Empire (everywhere)
Bay Area Steam Federation
Sacramento Steampunk Society
NYC Steampunks
Steampunk Chicago 
San Diego Steampunk
Portland Steampunk Society
Seattle Steamrats
Steampunk Society of Massachusetts
Steam Century Minnesota 
Texas Steampunks
North Florida Steampunk
Steampunk Los Angeles
Tampa Steampunk
Washington DC Steampunk Society
Toledo Steampunk
Manhattan Kansas Steampunk Society 
Gaslamp Society (Fresno)
Airship Archon (Columbus) 
Mid-Atlantic Steampunks
New England SteampunksLouisville Steampunk
New Orleans Steampunk AmericansDenver Victorian and Steampunk Society
High Desert Steam (Northern Nevada)