Answers.com is an online database of information and articles on a wide range of subjects.  With a well-deserved reputation for hosting reliable and accurate information, it is an essential research tool for authors.

Ever found yourself stuck coming up with a name for your characters?  If so, this is the site you need.  Behind the Name is a vast multi-cultural dictionary of names and their meanings.

A useful archive of common mistakes made by writers and the correct use of words and phrases.  This site lists the most common mistakes made by writers and provides an explanation as to why that usage is incorrect.

A joint project of the Electronic Frontier Foundation, Harvard Law School and others, to help writers understand and use their First Amendment and intellectual property law rights.

An online dictionary with a range of other valuable features, all of which are essential for writers, including a free translator, thesaurus, encyclopedia and much more.

A dictionary of slang terms and colloquialisms.  The dictionary includes slang terms from the UK and US, as well as a large links section to sites with slang from other countries and specialist slang dictionaries (e.g. prison slang).

The Dr Grammar site is no longer updated due to the death of its creator, but the FAQs section is still a useful guide with a list of common mistakes and explanations regarding the correct use of words and phrases.

An extremely valuable resource for authors, with articles describing how to do just about anything.  The articles are organised into easy to use categories and subcategories, helping you to quickly find the information you need.

With over seven thousand articles, this award-winning encyclopedia is an essential guide to mythology, folklore and religion, complete with an image gallery of deities, heroes and monsters.

Fiction Factor is an online magazine for writers that hosts a number of articles and features about writing, some of which are listed in the "Other Articles" section above.

A virtual library of significant websites created for a wide range of visitors, but for authors this can serve as an important research tool, allowing you to find useful sites with the information you need.

A useful site that uses multiple sites/resources to help you not only to translate text into your chosen language, but also to identify languages or even translate whole webpages.

Need to know what happened on a certain day in history?  This site gives you information for each day of the year about historic events, famous birthdays, music, television and more.

Need a famous quotation?  Then this is the site for you.  Drawing on multiple resources, this site has a wide variety of quotations available to access through a variety of means, including a keyword search.

Part of the dictionary.com family of sites, reference.com is a valuable resource for authors with an extensive online encyclopedia that's certain to be of use should you need more information on just about any subject.

A collection of extremely useful resources for poets compiled and created by the Shadow Poetry site, including information about poetic forms and the mechanics of poetry.

Part of the dictionary.com family of sites, thesaurus.com is an extensive online thesaurus with multiple alternatives for almost any word that's certain to assist you out whenever you're lost for words.

Need to brush up on your history?  This site catalogues historic events through timelines from the Big Bang to the present day, with interesting tidbits of information distributed throughout.

An online encyclopedia with a massive database of articles.  Even though just about anyone can edit almost any article in the database, the information is extremely accurate, making this site a valuable research tool for authors.