Definition:

Citation management tools enable researchers to capture bibliographic information about research materials, create bibliographies, add footnotes, and manage research collections.  Some citation management tools also make it easy to share references with other researchers.

Tools:

• BibDesk: "BibDesk is a graphical bibliography manager for OS X, providing powerful BibTeX file management for Mac users." (Free, Macintosh)
• BibMe:  Free web-based bibliography maker generating MLA, APA, Chicago and Turabian citations
• Bibus: Open source "bibliographic and reference management software" that is designed for collaboration, hierarchical organization of resources, and live query of medical databases such as PubMed (Free, cross-platform)
• Bookends: Reference manager with support for retrieving bibliographic information and related files from the Web, automatically generating bibliographies, etc. (Commerical, Macintosh)
• CiteULike: "A free online service to organise your academic papers." (Free, web-based)
• Connotea [Review]: "Free online reference management for all researchers, clinicians and scientists" 
• (Free, web-based)
• EndNote: "EndNote for Windows and Macintosh is a valuable all-in-one tool that integrates the following tasks into one program: Search bibliographic databases on the Internet; organize references, images, PDFs and other files; construct your paper with built-in manuscript templates; watch the bibliography and figure list appear as you write" (Commercial; Windows and Macintosh)
• Heurist: A collaborative academic bookmarking, bibliographic and general database with rich data types, annotation, record interlinking and publication capabilities, including bibliography output and citation within Word. Reference import and bookmarklet (Free, web-based, Open Source planned 2009)
• OttoBib: Enter an ISBN number and receive a formatted citation (Free, web-based)
• Papers: "Papers bundles all the great technologies that come with Mac OS X to give you a completely new workflow for reading scientific articles. You seek, download, archive, and organize all your articles within a single application. But that is just the start, using spotlight you instantly find the paper you are looking for. Read it fullscreen, add your notes, send a copy to a colleague..." (Commercial; Macintosh)
• RefWorks [Review]: "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." (Commercial; Web-based)
• Sente: "Sente 5 is the next-generation academic reference manager. Sente helps you find, organize, review and cite the academic literature in your field, and it does it in ways that you have probably not thought possible before. Sente also helps you build and maintain your library of PDF files for these references....Sente also excels at properly formatting bibliographies in your papers" (Commercial; Macintosh)
• Zotero [Review]: (Free; Windows, Macintosh and Linux; requires Firefox browser)

Resources:

• Comparison of Reference Management Software: Wikipedia article with summary information twenty different citation management tools, including cost, license, import/export formats, citation and reference list formats, word processor integration, and ability to connect to external databases.