Moody's Collectibles sells vintage postcards, but they also make available a huge catalogue of their stock. You can browse geographically by US State, by country, and by topic. Or, you can search for anything from alligators to the California Zephyr. They also have a blog. [more inside]
A nice set of photographic glass-plate transparencies depicting life in Japan ca. 1910. These "Yokohama photographs" were sold to foreign tourists between about 1868 and 1912. I found the Crafts and Trades section most interesting.