Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.

Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.

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.

Diigo - Diigo is a powerful research tool and a knowledge-sharing community

Weava - Workspace to highlight, organize & collaborate on your research articles.

JabRef - Graphical Java application for managing bibtex (. bib) databases.‎JabRef · ‎JabRef Help · ‎JabRef | Blog · ‎OpenOffice/LibreOffice .