The Bielefeld Academic Search Engine, from Bielefeld University Library (Germany), searches though more than 71 million open access documents in more than 3,000 repositories across the globe.
Aids in "the digital dissemination of more than 3,000 journals, books, reference works, and proceedings," from Stanford University.
Directory of OA Scholarly Resources. An international collection of 11,000 OA journals, conference proceedings, and other scholarly works that have been assigned an ISSN (International Standard Serial Number) from UNESCO.
The Open Access Infrastructure for Research in Europe project is an EU-based initiative to collect in one place "the entire Open Access scientific production of the European Research Area." They now provide access to more than 11.5 million publications from almost 6,000 repositories in EU member countries.
Academic books published open access are subjected to the same stringent levels of peer review and editing as those published traditionally. The resources below include descriptions about their peer review process.