Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
EndNote - Accelerate Your Research. Save time, stay organized, collaborate with colleagues and get published with EndNote 20.
JabRef - Graphical Java application for managing bibtex (. bib) databases.JabRef · JabRef Help · JabRef | Blog · OpenOffice/LibreOffice .
Qiqqa - Qiqqa is a free research and reference management software. It can be used in many organizational projects from the academic to the personal to the business endeavor. Read more about Qiqqa.
Papers by ReadCube - ReadCube Papers is a sumptuous reference manager helping out academic writers to get the most out when it comes to access and discovering more citations with multiple libraries or databases.