The National Diet Library announced on the 27th that they will soon be uploading around 15,700 volumes of Taisho era documents whose copyright term has recently expired. The documents, representing 17% of the library’s holdings on that period, will be available for free online starting July 3. The Diet Digital Archive web site, including the new material soon to be added, contains around 143,000 documents of material. While the archive contains large amounts of visual material such as photographs in addition to text, the web site and search tools are only in Japanese, so unfortunately non-Japanese readers will only be able to appreciate these sorts of items if Japanese readers find them and provide direct links.
I haven’t looked around yet, but I expect I’ll find all sorts of interesting things when I do. If anyone finds anything particularly cool, feel free to comment about it below.