Free (gratis) access to many articles in current "TOP25" lists. Filter by subject area and, within a subject area, by journal. Top 25 lists (earliest archive) are available by quarter (Jul-Sep 2004), academic year (2009-2010), and calendar year (2011).
Lists open Access reprints from Michigan Publishing available online (at HathiTrust) or for purchase from Amazon.
Textbooks for Arabic courses (all levels, some specific to regional varieties) account for the bulk of the list. The remaining books are a mix from fields including psychology, political science, health sciences, and business management.
"The SPO Scholarly Monograph Series is an interdisciplinary collection of original, open-access scholarly monographs and essays published by the Scholarly Publishing Office of the University of Michigan Library."
List of current open access titles is at the bottom of the page. All are published under the Creative Commons Attribution-Non Commercial-No Derivatives 3.0 license.