Zotero http://www.zotero.org/
Zotero is a free tool that allows you to gather and organize research sources from online catalogs, web sites, and journal databases. Sources can be organized into folders, and links, tags, and searchable notes can be added. Zotero also works in conjunction with Microsoft Word, to allow easy insertion of parenthetical citations and the creation of bibliographies in APA, MLA, and Chicago styles.
ZoteroBib http://zbib.org
ZoteroBib s a free and easy way to create bibliographies made by the creators of Zotero. It can create bibliographies in 9,000 different styles that you can copy and paste into your paper. Unlike the full version of Zotero, there is no need to download any software to your computer. It can be a good option if you just need to quickly create a bibliography.
BibMe http://www.bibme.org/
Bibme is a free online citation generator for MLA Style only that will find all of the bibliographic information for your source through a title or ISBN search or you can enter citation information manually.
KnightCite http://www.calvin.edu/library/knightcite/
KnightCite is an free online citation generator service, developed by the Hekman Library of Calvin College. It provides fill-in forms for the most common types of sources, and outputs the citation in either MLA, APA, or Chicago style. It is a quick, easy-to-use source for formatting citations.