Wikipedia

Wolfram Alpha is a "Computational Knowledge Engine" - different from a search engine, it answers factual queries directly by computing the answer from structured data, rather than providing a list …

Wikia is a community-based service that allows anyone to create a wiki on virtually any subject. Discover, share and add your knowledge! Wikia is financed by advertisment!

Reference.com offers a massive online dictionary, thesaurus, encyclopedia, quote finder, and translator (powered by Google Translate)- all for free. For the Dictionary.com and Thesaurus.com mobile app, go here....

The Encyclopædia Britannica is a general English-language encyclopaedia published by Encyclopædia Britannica, Inc., a privately-held company. The articles in the Britannica are aimed at educated...

Dixio is the solution for all those who care about their language Who want to learn more and enrich their vocabulary: when you receive a presentation or prepare a document, …

Referata offers hosting of semantic wikis, allowing you to add, structure and store data so it can be managed, shared, browsed and analyzed in as many ways as you choose. …

We find similar sentences to those in Wikipedia, complete with their citations for you to paste into your essay. It's the easy way to branch off to find authoritative sources …

Stubia is a mobile encyclopedia that limits each article to 160 characters: this limitation makes each topic easy to understand.

User-editable encyclopedia for fans of anthropomorphic animals. Over 12,000 articles on furry community and culture in eighteen languages.

A collaborative wiki of lists. Lists support images, maps, file attachments, as well as revision history. All lists and items can receive votes and comments, and the highest voted lists …

Encyclopedia.com – Online dictionary and encyclopedia with pictures, facts, and videos. Get information and homework help with millions of articles in our FREE, online library.

A wiki-based encyclopedia, the primary difference between Citizendium and Wikipedia being that Citizendium has "subject matter expert" editors, chosen by the community to validate pages and content.