The MLA Style Center: The MLA Style Center offers resources published by the Modern Language Association to help writers. This site includes a page with information about updates in the 8th edition of the MLA Handbook, as well as a quick guide to creating a Works Cited page and a guide for setting up a research paper.
APA Style CENTRAL: APA Style CENTRAL is published by the American Psychological Association and offers a number of resources for applying and using APA Style. The site has quick guides, samples, tutorials, and quizzes to help writers.
Chicago-Style Citation Quick Guide: The Chicago-Style Citation Quick Guide is published by the University of Chicago Press and is an official accompaniment to The Chicago Manual of Style. This quick guide offers writers sample citations for various types of sources, demonstrating both proper notes and proper bibliography entries for sources.
Purdue Online Writing Lab: The online writing center at Purdue University has an amazing library of 100 handouts on common writing problems.
References, Thesauruses, and Dictionaries
Bartleby.com / Great Books Online: Bartelby.com offers many literature classics online (in their entirety), for free. This site also offers on-line editions of dictionaries, thesauri, encyclopedias, quotations and style guides by such language mavens as Strunk, Mencken and Sapir.
APA Style Blog: The APA Style Blog is a companion to the official APA manual. The blog covers a number of tricky APA style and citation questions that may not fall neatly into a category covered in the APA manual, and the blog is also written in clear, easy-to-understand language.