Citation Management Tools

Reference management software, citation management software or personal bibliographic management software is software for scholars and authors to use for recording and utilising bibliographic citations (references). Once a citation has been recorded, it can be used time and again in generating bibliographies, such as lists of references in scholarly books, articles and essays. The development of reference management packages has been driven by the rapid expansion of scientific literature.

The following software is the most used but you can find more with a simple web search.

Endnote
"...use EndNote to search online bibliographic databases, organize their references, images and PDFs in any language, and create bibliographies and figure lists instantly."

Endnote Web info
EndNote Web, a component of Thomson Reuters EndNote and Web of Knowledge, is a Web-based reference organizer and collaboration tool that enables EndNote users to collect references when away from their desktop, and collaborate easily with others. The combination of EndNote with EndNote Web and Web of Knowledge provides researchers with an integrated solution for research and writing.

Note: You can access EndnoteWeb by registering in ISI Web of Knowledge

Refworks
"an online research management, writing and collaboration tool -- is designed to help researchers easily gather, manage, store and share all types of information, as well as generate citations and bibliographies."

Mendeley (free)
"Mendeley Desktop is academic software that indexes and organizes all of your PDF documents and research papers into your own personal digital bibliography. It gathers document details from your PDFs allowing you to effortlessly search, organize and cite. It also looks up PubMed, CrossRef, DOIs and other related document details automatically. The drag-and-drop functionality makes populating the library quick and easy. The Web Importer allows you to quickly and easily import papers from resources such as Google Scholar,ACM, IEEE and many more at the click of a button."

Zotero(free)
open source add-on for the Firefox browser. Zotero enables users to manage bibliographic data and to store web-page snapshots and other electronic objects. Through a separate add-on, it also allows citation in text (in Microsoft Word and OpenOffice Writer) and can automatically create bibliographies in various formats (such as APA and MLA).