Bevatron - A photo-essay about the Bevatron, a venerable and recently decommissioned accelerator at the Lawrence Berkeley National Laboratory.
Caldecott Tunnel Tour - A photo tour of a car tunnel that "cuts through the East Bay Hills from Oakland to Lafayette, taking Highway 24 with it".
Friends Of Vast Industrial Concrete Kafkaesque Structures - An interesting site offering industrial archaeology along the course of the Los Angeles River flood control channel.
Haloed Moment - Photos and write-ups of various exploratory locales around the state, including the UCLA and UCSD steam tunnels.
Industrial Archaeology - This picture archive is a different site from "Industrial Archaelogy in California", although it is also in California.
Industrial Archaelogy in California - Abandoned buildings in Richmond, Berkeley, Oakland and San Jose.
Institute for Urban Exploration - An old Floridian website and forum, now revived and established in San Francisco.
Homepage of the California Association of Mine and Cave Explorers - Site of a group that aims to tour mines and missile silos without trespassing.
Public Health Service Hospital - A collection of photos of a very large abandoned San Francisco hospital.
San Francisco Batteries Virtual Tour - Climb on, around and under disused fortifications and tunnels near San Francisco.
San Francisco Sewer Tour - A commemoration of SF Cacophony's very fancy 1990 sewer tour.
UCLA Tunnels - An out-of-date but still useful site on steam tunnels under the University of California at Los Angeles.
UCSD Tunnels - An out-of-date but still useful site on steam tunnels under the University of California at San Diego.
Urban Photography Commandos - Although their efforts are not limited to cities, the UPC site features some nice photos of abandoned buildings and military leftovers in California.