TinyCat - The online catalog and integrated library system for tiny libraries, powered by LibraryThing.
Atoll Digital Library - Atoll Digital Library is an open source platform for building digital library collections.
DSpace - DSpace open source software enables open sharing of content that spans organizations, continents...
FOLIO - Simple version control app for designers based on Git
Invenio - Invenio is a free, open-source software to run a digital library or document repository on the web.
BiblioteQ - BiblioteQ strives to be a professional cataloging and library management suite. The SRU and Z39.