The word is out about the neat project a couple have done at oldsf.org. While the San Francisco History Center at the San Francisco Main Library has had much of their historical photograph collection online for years, “oldsf” has scraped the data so you can view thumbnail images on a map on their site.
No more searching for “18th Avenue” then “19th Avenue,” etc. Just click on the arrows in an area. And you can narrow your options by date. Very neat. Check it out.