How Stuff Works www.howstuffworks.com

Articles explain how hundreds of things work, from elements of the human body to space-age technology.

Xrefer www.xrefer.com

Search for free across a wide range of encyclopedia, dictionaries, thesauri, quotations and biographies. Most entries feature multiple cross-references.

Encyclopedia Mythica www.pantheon.org

Over 6,000 entries on mythology, folklore and legend. Includes some images and stories.

Quisdom www.quisdom.com

Encyclopedia of trivia. Includes definitions of acronyms and abbreviations, flags of the world, entertainment milestones, concise information about sports and religion.

Probert Encyclopedia www.probert-encyclopaedia.co.uk

Serious reference source with over 60,000 fully hypertext linked entries covering the entire spectrum of human knowledge.