Up to 50 sheets of Russian 3-verst map (1:126,000) have been added, courtesy of the digital library of the Jagiellonian University, Krakow, and the Library of Congress. Also, after some painstaking effort, it hs been possible to make those maps, as well as the WW1 German variants, available through index sheets; consequently, these maps are now easily available through Mapster place-name search engine.
Several other index sheets have been created, including a mid-19th century Polish "Mapa Kwatermistrzostwa” (1:126,000) from the digital archive of the National Library, Warsaw.

Problems with Mapster index sheets have now been fixed.
We have added up to 50 sheets of the Austrian (KuK) "Operationskarte" 1:400,000. The 300 dpi sheets come from a digital library of the Polish Academy of Science, those at 400 dpi are from private collectors and, through help of  easteurotopo.org site, from the Library of Congress.
We have also added a few town plans: Köslin (Koszalin), Belgard (Bialogard), Sopot – all in the Pomorze (Pommern) area of Poland, Kostrzyn (Küstrin), and Klaipeda (Memel). More (many more) town plans will be made available after summer.

We have separated older editions of WIG 1:25,000 maps, which are divided according to the original materials (German, Austrian and Russian). These older sheets from 1920s can be found on a separate index sheet. We have added 6 new sheets of the older, and 14 sheets of the new (1930s') edition. All new scans at 600 dpi. A few dozens older type sheets from the area of former Austrian "partition" should become available by mid-summer.
Courtesy of Katedr Geologii i Geografii, Uniwersytet A. Mickiewicza Poznan, Poland, we have received  28 sheets of a German 1:25,00 soil / land valuation map dated 1940 - 1944. These maps are based on Polish 1:25,000 (WIG) maps, German Topographische Karte (Messtischblatt) and Russian verst maps. We might be able to add a larger number of sheets of this map type by end of this year.
There's been an update to the page with index sheets of WIG maps.
Semi-related news (for those with a passion for scanning large maps on a small-format scanner): Panavue, a long-standing software provider for stiching photographs (and maps) are closing down by September 2014. In the meantime they have made their flagship (enterprise) stitching software available for free. On their home page you will find a link to the download page. Installation is fast and painless, no strings attached, e.g. giving up personal data, registration, etc. Software can be installed in either English or French language version. While the interface is a bit dated, and the stiching does not always provide perfect results, this is still one of the best programs of this type available (no, they didn't pay us to say that).

Courtesy of the Library of Congress, through hard work of volunteers from the easteurotopo.org site, we have been able to add 280 sheets of the Russian (and Soviet) 2-verst maps (1:84,000), mainly from the territory of Lithuania, Belarus, Ukraine. All sheets 600 dpi, majority dated 1922 - 1934. Several sheets available in two different editions (updates are visible on some of them). All new sheets have been marked in green ("new").