Zotero
Zotero is an open-source citation manager available in a browser or desktop version for Mac, Windows and Linux. It's a good option for collaboration and group work in the classroom. Documentation and screencasts can be found here.
RefWorks has full-text management and collaboration features. In addition to dozens of bibliographic output formats, you can install custom output styles as well as create new bibliography items from scratch.
*On October 6, 2026, RefWorks will become EndNote Fusion. No action is required on the part of RefWorks users.
Write-N-Cite is a plugin that allows you to run an abbreviated version of RefWorks in Microsoft Word.
EndNote
This tool is both an installable, desktop version as well as a companion web page. You can search several databases within EndNote.
EndNote training material can be found here.
Mendeley
Mendeley provides a variety of features including the ability to read and annotate pdfs within software, collect and organize pdfs, share your papers' notes, and discover new papers, people to collaborate with and groups.
See the Research Toolkit for more information, including How do I use sources in my paper?