BASE is one of the world's most voluminous search engines especially for academic open access web resources and is operated by Bielefeld University Library.
A important feature of BASE is to discloses web resources of the "Deep Web", which are ignored by commercial search engines or get lost in the vast quantity of hits.
The primary aim of DOAB is to increase discoverability of Open Access books. The directory will be open to all publishers who publish academic, peer reviewed books in Open Access and should contain as many books as possible, provided that these publications are in Open Access and meet academic standards.
DOAJ is an online directory that indexes and provides access to quality open access, peer-reviewed journals.
EconStor is the Open Access server of the German National Library of Economics – Leibniz Information Centre for Economics. EconStor provides a basis for the free publication of academic literature in economics.
OAPEN provides a platform for the full text dissemination of Open Access books. OAPEN builds a quality controlled collection of Open Access books, mainly in the area of Humanities and Social Sciences, and develops services for publishers, libraries and research funders in the areas of dissemination, quality assurance and digital preservation.
RePEc (Research Papers in Economics) is a collaborative effort of hundreds of volunteers in 96 countries to enhance the dissemination of research in Economics and related sciences. The heart of the project is a decentralized bibliographic database of working papers, journal articles, books, books chapters and software components, all maintained by volunteers. The collected data are then used in various services that serve the collected metadata to users or enhance it.