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. (Cornell Library's comparison chart)
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 2/11/2016 (47 min).