Online Resources for Writers

Project Bartleby
Grammars, Dictionaries, and Other Guides
Style and Usage
English as a Second Language Pages
Lists of Writing Links

Columbia University's Project Bartleby publishes classic works whose copyrights have expired:

Professor Darling publishes an excellent online Guide to Grammar and Writing, complete with quizzes. He provides useful mini-courses on grammar and mechanics. Miss Grammar's cousin — the elderly, but vigorous, "Grammar" — resides there too.
Rutgers professor, Jack Lynch, publishes a handy Grammar and Style Notes, based on his classes.
An Elementary Grammar will have you talking about the future perfect tense and conjunctive adverbs in no time. Sponsored by "The English Institute," a British training organization, this site focuses on English as a Second Language.
The List of Dictionaries provides links to many online dictionaries and word books, including dual-language works (English-German, for example) and non-English language books.
Hypertext Webster Interface. This engine lets you access the various Webster's dictionary services on the Internet. Just type in a word, and the definition will appear!
ROGET'S Thesaurus Search Form, an experimental program maintained by Mark Olsen at the University of Chicago, lets you "search the headwords or full text of Roget's Thesaurus."
Jeremy Smith's British-American Dictionary documents the truth of the adage that England and America are two nations separated by a common language. For another amusing illustration of this truth, see United Kingdom English for the American Novice, in which one learns that "American dinner" means potluck.

In case you missed this classic in school, here is George Orwell's 1946 essay on writing clearly: Politics and the English Language.
Jonathan Price of the Communication Circle offers Tips to tighten up your Web prose—and most other writing too.
Mark Israel's FAQ File on English Usage (from the news group alt.usage.English) is a "rich" site, but not a hypertext document.
The Editorial Eye Index lists a sampler of articles originally printed in the "Eye's" monthly newsletter.

The English as a Second Language Home Page, from the University of Illinois at Urbana, offers very useful links to language lessons (including downloadable audio and video), cultural information, and much more. Its link categories include "Listening and Speaking," "Reading," and "Writing." It is maintained by Rong-Chong Li, who also researches and develops computer-assisted language-learning programs.
ESL Web Guide boasts over 2500 links in these categories: Grammar; Writing; E-mail; Listening; TOEFL; Pronunciation; Home pages; News; Vocabulary; Reading; Magazines; Games; Dictionaries; Poetry; Schools; Music.

The Writers' Resources links you to information on nearly every genre and mode of writing, from business memos to children's stories.
Garbl's Writing Resources On Line features Gary B. Larson's "annotated directory of web sites focusing on English grammar, style, usage, plain language, words, reference sources, online writing experts, active writing, word play and books on writing."
Purdue University's Writing Resources and Writing Labs on the Net provides extensive information and numerous links.