Mendeley is online software for use in citation management - that is, keeping your cited references (books, articles, etc.) organized and properly formatted so they can be included in your finished paper.
Important features and things you need to know about Mendeley:
Want to learn more about different citation management software? Take a look at this chart (note that features of different programs change all the time; we do our best to keep our information current, but be sure to look at the documentation and websites for these programs themselves to be sure).
Zotero is a powerful, easy-to-use research tool that helps you gather, organize, and analyze citations and sources such as pdfs and Web sites, and then share the results of your research.
It's open source and free. It's one of a number of citation and information managers. (see Cornell Library's comparison chart)
See also this list of upcoming Zotero Workshops offered by the Cornell University Library.
Get a preview of our workshops and an introduction to Zotero by viewing a WebEx recording from 1/28/15 (52 min).