Official site of the Encyclopedia Britannica, one of the world's best-known reference books. Find short encyclopedia entries and definitions, or register for complete access.
English-language version of Wikipedia, the online encyclopedia built and edited by users. Find encyclopedia entries on almost any topic, or click for a random Wikipedia article.
User-created encyclopedia, web directory, and knowledge web. Everything2 offers definitions, articles, and writeups by readers about anything and everything.
Searchable online version of the 1911 Encyclopedia Britannica, containing 29 volumes and articles written by more than 1500 authors on topics from A to Z.