Mendeley - Easily organize your papers, read & annotate your PDFs, collaborate in private or open groups, and securely access your research from everywhere.
Citavi - Citavi is a program for Microsoft Windows that manages literary references and organizes organizational knowledge.
Zotero - Zotero is a free, easy-to-use tool to help you collect, organize, cite, and share research.
Auratikum - Auratikum helps you organize, structure and innovate your writing project.
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.
Docear - Docear