Collins Dictionary
Collins Online Dictionary: definitions, thesaurus, translations, synonyms, pronunciations, word origin and much more.
Dictionary.com
Find English definitions, synonyms, word origins, audio pronunciations, example sentences, slang phrases, and more at Dictionary.com.
Encyclopaedia Britannica
Encyclopedia Britannica: a fact checked online encyclopedia with biographies, videos, images and much more.
Encyclopedia.com
Encyclopedia: a meta encyclopedia with free access to citeable source reference entries.
FactMonster
Factmonster.com: Fact Monster combines essential reference materials, including an encyclopedia, dictionary, thesaurus, and atlas, fun facts and features.
Grammar
Find a free grammar spell checker, grammar tutorials and much more at Grammar.com.
Merriam Webster Dictionary
The dictionary by Merriam-Webster is an online dictionary offering word definitions and pronunciation for the English language.
Synonyms
Free online thesaurus with synonym and antonym definitions for many languages, including visual diagrams, audio pronunciations, translations, etymologies, usage examples and much more.
The Rosetta Project
The Rosetta Project: a collection of the world's greatest literature, known cures of diseases, technology blueprints, over 1,000 human languages and much more.
Wikimedia Commons
Wikimedia Commons: a searchable database of free media files, including images and videos anyone could use and contribute to, including public domain images, free to use images with other forms of licensing, photo challenges and much more.
Wikipedia
An encyclopedia where users create and edit encyclopedia pages.
Word Reference
Word References. Free online dictionaries, including Spanish, French, Italian, and German dictionaries. Conjugations, audio pronunciations and message boards.