Onelook - One word describes OneLook: comprehensive, as in covering completely. This site collects definitions from more than 100 dictionaries.
WWWebster Dictionary - From the time-honored Merriam Webster company.
The Alternative Dictionaries - "These pages contain words and expressions you most likely won't find in a normal dictionary" including slang, insults, racial slurs, and terms for bodily functions and sexual acts. "
DICT  - Uses "...several freely available dictionary databases, with over 300,000 total headwords..." Ongoing project.
LOGOS  - Multi-language translating dictionary.
ARTFL Dict. - "1913 Webster's Revised Unabridged Dictionary"
Web of Online Dicts. - "...linked to more than 1,000 dictionaries in 200 different languages."
Slanguage Dictionary - All those words that give English it's flavor.
Online ASL Dictionary - A visual dictionary of American Sign Language. Some things can only be said in pictures, and this site uses animated photographs to display the beauty and meaning of sign language words and phrases.
Symantic Rhyming Dict.  - "...use it to help write poetry, song lyrics, greeting cards, witticisms, and more."
Roget's Thesaurus - Use a categorical or alphabetical index or a search form .
Biographical Dict. - "...more than 27,000 notable men and women who have shaped our world"
biographie.net - Biographies across the web in 4 languages.
Biography - "...puts over 20,000 of the greatest lives, past and present, at your fingertips."
Acronymfinder - When you need an acronym PDQ, check Acronym Finder. 
Acronyms and Abbreviations  - Very fast searcher and useable even with Lynx.
Quote Search - Search options include multiple quotations databases.
Anagram Generator - "Over 1143888 anagrams served!"
Wordsmyth Educational Dictionary-Thesaurus - "...dictionary and a thesaurus with powerful and flexible search capabilities."
Fonetiks.org: the Online Language Laboratory - Want to learn to speak Thai or Brazilian Portuguese? This online language laboratory can help. It features easy to use audio tutorials on some of the world's major languages.
Online ASL Dictionary - A visual dictionary of American Sign Language. Some things can only be said in pictures, and this site uses animated photographs to display the beauty and meaning of sign language words and phrases.
Poetry Daily - A new poem every day, news, and a poetry archive make this site worth a visit and a bookmark.
Poets.org: Listening Booth - Poetry is best when read aloud. Head to the listening booth to hear music made from words. You will need the RealPlayer.
Surname Search - "Trace the History of Your Family Name"
Surname Search - Surname searches in four countries. (Multiple popups)
Researchpaper.com - A great resource for those needing inspiration. The site has tips and ideas to help with your writing. The site even includes a chat room so you can talk to other students.
CMU Pronouncing Dictionary - "...pronunciation dictionary for North American English that contains over 100,000 words and their transcriptions."
Bibliomania - Keyword search allows search through all or each of 5 categories or literature.
Symantic Rhyming Dict.  - "...use it to help write poetry, song lyrics, greeting cards, witticisms, and more."
Language Identifier - "...will attempt to identify automatically the language of a sentence, phrase, or word..."
Glossary of Genetic Terms - by the National Human Genome Research Institute: Division of Intramural Research. Learn the language of genetics! Listen to geneticists explain important genetic terms and view diagrams to help you understand human genetics.
Encyclopedia.com - "...more than 14,000 diverse articles to the resources available on Infonautics' popular online research service."
Dictionary of Symbolism - Explanations for commonly used symbolism in literature. Searchable.
BooksOn-Line by Author - 9000+ listings of online books. Search form or alpha directory.
BookBrowse.com - collects reviews, user opinions, substantial excerpts, and images of book jackets and author biographies.
Literary Resources on the Net - "An incredibly comprehensive collection of Web sites related to literature & the humanities. Includes Syllabi and Other Course Materials for Literature Courses." Searchable.
Gale's Literary Index - Doing a report on an author, or need to find literary criticism about a particular work of literature, but aren't finding any useful information on the Internet? This free index lets you search it by author or by title. Then it will tell you which reference books you can find the information in.
A Glossary of Literary Terms - Definitions and examples of literary terms. Compiled by an English professor.
Glossary of Poetic Terms from BOB'S BYWAY - An extensive collection of poetic terms and their definitions, with numerous cross-references and examples. Browsable by letter of the alphabet.
The Harvard Classics & Shelf of Fiction - "The most comprehensive and well-researched anthology of all time comprises both the 50-volume '5-foot shelf of books' and the the 20-volume Shelf of Fiction. Together they cover every major literary figure, philosopher, religion, folklore and historical subject through the twentieth century."
Humbul Humanities Hub - Searchable, browsable collection of Internet resources in the fields of: English, History, Philosophy, History & Philosophy of Science, Theology, Religion, Modern Languages.
The Internet Book Information Center - A guide to book and literature related Internet resources, arranged in a narrative style.
Literary Timeline - With this handy search tool, users can look up "significant literary events" for each day of the year.
Perseus Digital Library - An evolving humanities digital library. Presently collects materials on classics/antiquity, Victorian London, natural philosopher Robert Boyle, the history of Tufts University, and part of the Library of Congress-sponsored American Memory collections.