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.
Citavi - Citavi is a program for Microsoft Windows that manages literary references and organizes organizational knowledge.
EasyBib - Automatic works cited and bibliography formatting for MLA, APA and Chicago/Turabian citation styles.
BibSonomy - BibSonomy is a system for sharing bookmarks and lists of literature (BibTex format).
BibGuru - BibGuru is a bibliography and citation generator for students.