Transit and Trails
The Transit and Trails website has built a Google Maps mashup to show the locations of walking trails and parks around the San Francisco Bay Area. The site allows the user to find trails and plan your trip to the start and from the end back home using public transport.
Once you have selected a trail from one of the numerous markers on the map an information window opens with details of the closest public transit to this point. You can then get transit directions to the trail from any point from either Google Maps directions or 511.org.