The Columbia University Libraries has recently acquired a database of 400 digitized Yiddish books from the Hebraica and Judaica of the Tychson Collection at the Rostock University.
According to the publisher's description:
"The nearly 400 titles of this edition offer a cross-section of the history of Yiddish books up to the 19th century. There are numerous rarities and unica, including the first Yiddish printing, Mirkevet ha-Mishne, Krakau 1534. Among translations and paraphrases of the Bible the collection contains the Konstanz-edition (1544) as well as translations by Blitz and Witzenhausen. Three of the existing editions of the Tsene-rene (Frankfurt a.M. 1685, Sulzbach 1702) were first discovered in Rostock, and the third of those (Fürth [Pseudo-Amsterdam] 1761) is apparently to be found nowhere else. One of the rarities among the prayer-books is a Hebrew Siddur. It contains Yiddish passages and was published in 1560 in Mantua."
This resource provides access to some of the oldest and rarest printings of Yiddish materials in existence.
We will soon be adding records with direct links to each of the titles in CLIO for easier searching.
Note: The site is in German. To view a list of titles, go to: http://www.columbia.edu/cgi-bin/cul/resolve?clio10264881, and then click the link for "Titel" after "Die Hebraica und Judaica der Sammlung Tychsen und der Universitätsbibliothek Rostock" in the "Collections" box. You can also search by keyword. To access the PDF, click "Details" under the title that interests you, and then click "PDF" under "komplettes Werk." The link to PDF will then change to "Herunterladen," and you can click that to download the file.