Park and Trail Links
The Trail Center is a volunteer-driven organization that builds, maintains, and promotes trails in the San Francisco Peninsula and South Bay parks. The Trail Center site has an extensive list of links to park agencies and stewardship groups, plus a schedule of trail builds you can partipate in. www.trailcenter.org
Bay Area Hiker is an extensive online guide to Bay Area parks, open space, and trails. Author Jane Huber also includes reviews of maps and guidebooks and another great set of links to park agencies and related groups. http://www.bahiker.com
Bay Nature (www.baynature.org) is a natural history magazine focusing on the San Francisco Bay Area. This award-winning quarterly magazine includes feature articles on Bay Area ecology and habitats, and conversation issues. "On the Trail" articles (for which I do the maps) cover diverse parks as Montara Mountain and Elkhorn Slough.
Bay Area Ridge Trail Council (www.ridgetrail.org) has worked since 1989 on a 500-mile trail around San Francisco Bay.
Coastwalk (www.coastwalk.org) promotes the 1500-mile California Coastal Trail, and sponsors annual Coastwalk hikes in many California coastal counties.
Japantown and Cultural Landscape Links
The National Japanese American Historical Society (NJAHS) has a small gallery and extensive archives in San Francisco's Japantown. NJAHS was founded by a group of WWII veterans who served in the Military Intelligence Service in the Pacific theater and the Army's 442nd Division in Europe. Their focus has grown to include all aspects of the Japanese American experience. www.njahs.org.
Japantown Atlas (www.japantownatlas.com) is a site I created as part of a 2006 California Civil Liberties Public Education Program grant. Maps of 24 California Japanese American settlements as they appeared in 1940. A companion site is Preserving California's Japantowns (www.californiajapantowns.org)
Other Map Sources
(I'll flesh out this list as it comes to me...as one of just two map dealers listed in San Francisco (and I mainly deal my own; the other folks mainly deal in antique prints); I remember the week I got a call from a Californian looking for maps of Switzerland, and Swiss tourists looking for maps of central California. I had neither to offer! Then someone called looking for a globe.
Longitudemaps.com (retail arm of Eastlink Map Distribution) has a good collection of US and international maps, plus atlases.
International Travel Map Bureau (a great Canadian cartographic publisher does reliable color maps of South America, Asia, etc.)
For do-it-yourself map-searching online, I highly recommend Caltopo.com, which has Google, USGS, Open STreet Map, Canadian maps, and more, which you can view separately or together.
Avenza's Map Store is an iOS and Android app that is a good source for digital versionsn of printed maps including USGS maps, which fit neatly in your phone (even w/o a web connection when you later go out in the field).
Most park agencies have good websites and online maps now; much better than back in the day. I regularly do maps for Sonoma Regional Parks and San Mateo County Parks; for years I also did the web maps for Marin County Open Space District but they're doing well without me. A good place to look first.