Zotero, a freely available tool created by the Roy Rosenzweig Center for History and New Media (CHNM) at George Mason University, is the most popular citation manager among historians. The Rutgers Zotero Guide provides a good overview.
RefWorks is a Web-based bibliography and database manager that enables you to:
The DHI's home page links to a calendar of events and to DH projects at Rutgers. The New Brunswick Libraries also offers many workshops on DH tools.