EndNote Web: a Web-based service designed to help students and researchers through the process of writing a research paper. Undergraduate students can organize their references for citing in papers. Professional researchers and graduate students can use EndNote Web as the perfect complement to EndNote and other desktop writing tools, as well as storing references between ISI Web of Knowledge search sessions.
Zotero: an easy-to-use yet powerful research tool that helps you gather, organize, and analyze sources (citations, full texts, web pages, images, and other objects), and lets you share the results of your research in a variety of ways. It has the ability to store author, title, and publication fields and to export that information as formatted references and the best parts of modern software and web applications (like iTunes and del.icio.us), such as the ability to interact, tag, and search in advanced ways. Zotero integrates tightly with online resources; it can sense when users are viewing a book, article, or other object on the web, and on many major research and library sites find and automatically save the full reference information for the item in the correct fields.
citeulike: free service for managing and discovering scholarly references. It can easily store references you find online, discover new articles and resources, automated article recommendations, share references with your peers, find out who's reading what you're reading, and store and search your PDFs.
EasyBib (Write Smart): The free version of EasyBib formats citations in the latest edition of the MLA format (currently the 7th edition). To use EasyBib's APA formatting services, sign up for MyBib Pro by clicking here: https://www-secure.easybib.com/products/easybibpro.
KnightCite: an online citation generator service provided by the Hekman Library of Calvin College. This service simplifies the often tedious task of compiling an accurate bibliography in the appropriate style by formatting the given data on a source into a reliable citation, eliminating the need to memorize minute details of style for multiple kinds of sources. The service is provided free of charge by the college, and is available to members both within and outside of the Calvin community.
JabRef: an open source bibliography reference manager. The native file format used by JabRef is BibTeX, the standard LaTeX bibliography format. JabRef runs on the Java VM (version 1.5 or newer), and should work equally well on Windows, Linux and Mac OS X.
Son of Citation Machine: Professional researchers to properly credit the information that they use. Its primary goal is to make it so easy for student researchers to cite their information sources, that there is virtually no reason not to -- because SOMEDAY THE INFORMATION THAT SOMEONE ELSE WANTS TO USE -- WILL BE YOURS!