Save The Bay is the oldest and largest membership organization working exclusively to protect, restore and celebrate San Francisco Bay. As its leading champion, Save The Bay is committed to making the Bay cleaner and healthier and connecting residents to it.
On May 15, 1999, Dinesh Desai and Bob Cowell started walking a 425 mile loop following the ridges around SF bay. They finished on June 20 (Fathers Day). Allowing for a few rest days, I figure it took them about 30 days of actual walking.
During the month of October 2002, J.H. walked 300 miles in a loop around San Francisco Bay. He made audio recordings of ambient sounds along the way.
In 2003, Gillian Robinson and Don Lundell ran the Bay Ridge Trail in 13 days -- a total distance of 500 miles.
Peter and Donna Thomas walked from San Francisco Bay to Yosemite Valley.
Association of Bay Area Governments (ABAG). These folks are building the Bay Trail. Still not clear to me if they are going to create a loop around the bay. But they have good maps of existing and planned trails.
NEW AND HOT! The Bay Trail Planners have completed an analysis of gaps in the Bay Trail. Some great maps!
511.org This site links you to all the transit systems in the San Francisco Bay Area. Each county has a transit system. Most transit system have system maps. Some you can order free online. Some you have to call and they will send it. Some you have to look at each bus route link on the web to see what's going on. I hate that.
Bay Area Geenbelt Alliance: Protecting the San Francisco Bay Area's open space and promoting livable communities since 1958.
Can't leave out the patron saint of Bay Area hiking - Bay Area Hiker. Everything you ever wanted to know about hiking trails in the Bay Area. Includes links to maps for most hikes. Also check out the links page for list of walking groups.
A problem with trails in the more remote marshy areas is the difficulty of finding good maps. Those trails can twist and turn all over the place. Here is someone who has mapped all the levees and trails from Dumbarton to Sunnyvale.
Read up on SF Bay Nature:
Some links to various trail maps - Not on topic, but I like maps:
National Park Service Golden Gate Trail Maps.
A List of Hiking and Walking Groups