You can spend hours browsing this site, zooming in on various cross streets and points of interest. Here's a shot near our place that I love:
And here are a few more favorites...
16th and Valencia, in the Mission, 1927.
Sunset Branch Public Library, 1918. This is our neighborhood library, still standing!
Downtown San Francisco with Yerba Buena Island in the distance, 1921.
Two Women on the shore of Stow Lake in Golden Gate Park, 1869 (!).
I particularly love the images that have people or cars in them so you can see how styles have changed over the years. This image in Golden Gate Park strikes a particular chord with me because the boy and I take many walks around this lake and do a little in-city hiking up the "mini mountain" in the middle. There's some killer stairs and a waterfall view as your reward.
I hope you'll enjoy this site as much as I do. It's addictive, so don't say I didn't warn you.