Zotero is a free, easy-to-use tool to help you collect, organize, share research and cite your research sources directly in your favourite word processor, with 300 MB free online storage.
Mendeley helps manage and share academic knowledge: Mendeley Desktop is free academic software (Windows, Mac, Linux) for organizing and sharing research papers and generating bibliographies with 1GB of free online storage to automatically back up and synchronize your library...
Weava is a collaborative workplace for research offering an easy way to highlight, organize and collaborate on your research articles.
Automatic works cited and bibliography formatting for MLA, APA and Chicago/Turabian citation styles. Now supports 7th edition of MLA.