Zotero is a free tool designed to help you gather, manage and share information about books, articles, web pages and other digital objects that you are using in your research, and to generate citations and bibliographies. Zotero is a Mozilla browser plugin. You can choose to gather your data on your hard drive (if you are working mainly from one computer), or on a flash drive or a network (if you frequently access your data at multiple workstations).
Mendeley is a free reference manager and academic social network that can help you organize your research, collaborate with others online, and discover the latest research. You can automatically generate bibliographies, collaborate with other researchers online, import papers from other research software, find relevant papers based on what you’re reading, and access your papers from anywhere online.