Many different online encyclopedia projects have been proposed.

In 1993, a project called Interpedia was being discussed; it was planned as an encyclopedia on the Internet to which everyone could contribute materials. The project never left the planning stage and it was overtaken by the explosion of the World Wide Web and the emergence of high-quality search engines.

The most profound output of these might be the early proposals, especially from the Millennium Project of the United Nations University in 1993, to filter the material for religious and ethical alignments that might make it easier to manage the divergence of values in any global project.

Anticipating major problems too early may have been one of the reasons these projects did not succeed. Converting existing material was less controversial.

Digitization of old content

A key branch of this activity is the digitization of old printed encyclopedias. In January 1995, Project Gutenberg started to publish the ASCII text of the Encyclopædia Britannica, 11th edition (1911), but disagreement about the methods halted the work after the first volume. In 2002, ASCII text of all 28 volumes was published on http://1911encyclopedia.org/ by another source; a copyright claim was added to the materials, but it probably has no legal validity. Other digitization projects have made progress on other titles. One example is Easton's Bible Dictionary (1897) digitized by the Christian Classics Ethereal Library. Probably the most important and successful digitization of an encyclopedia was the Bartleby Project's online adaptation of the Columbia Encyclopedia, Sixth Edition, 2000, which was put online at http://www.bartleby.com/65/ in early 2000 and is updated periodically.

Creation of new content

Another related branch of activity is the creation of new, free contents on a volunteer basis. In 1991, the participants of the Usenet newsgroup alt.fan.douglas-adams [1] started a project to produce a real version of The Hitchhiker's Guide to the Galaxy, a fictional encyclopedia used in the works of Douglas Adams. It became known as Project Galactic Guide. Although it originally aimed to contain only real, factual articles, policy was changed to allow and encourage semi-real and unreal articles as well. Project Galactic Guide contains over 1700 articles, but no new articles have been added since 2000; this is probably partly due to the founding of h2g2, a more official project along similar lines.

Encyclopedias that are no longer online

• Interpedia
• Nupedia, a slow-moving project to produce a free peer reviewed encyclopedia. Nupedia shut down on September 26, 2003, and much of its content has since been assimilated by Wikipedia.
• Gnupedia, an initiative which didn't come to fruition but had some interesting philosophy.

Currently online encyclopedias

• Wikipedia
• Ekşi Sözlük -- an older Turkish variant with the same concept as h2g2
• Project Galactic Guide -- an older project inspired by The Hitchhiker's Guide to the Galaxy.
• Everything2 has a wider range and does not exclusively focus on building an encyclopedia; its contents are not available under a copyleft license.
• h2g2, a collection of sometimes humorous encyclopedia articles, based on an idea from Douglas Adams's The Hitchhiker's Guide to the Galaxy. Articles are not freely redistributable.
• EvoWiki is "a Wiki about evolution and origins. The focus is on evolution education, particularly addressing the arguments of Creationism and Intelligent Design from the perspective of mainstream science. It is inspired by webpages such as talkorigins.org and talkdesign.org, and the goal of EvoWiki is to complement rather than duplicate these online resources".
• Disinfopedia, a project to expose propaganda and paid spin doctors.
• Consumerium, a project to provide consumers with product information and increase the power of the consumer in a market economy.
• Wikitravel, a free travel guide started in July 2003.
• Yellowikis aims to be to Yellow pages what Wikipedia is to the Encyclopædia Britannica.

Several online encyclopedias focus on mathematics:

• MathWorld, a proprietary system hosted at Wolfram Research.
• PlanetMath is a free Wiki-style mathematical encyclopedia which was originally built to replace MathWorld, a proprietary system hosted at Wolfram Research which was down for some time due to legal difficulties. Since MathWorld has returned, PlanetMath has still thrived.
• The QED Project is building a "distributed, computerized repository that rigorously represents all important, established mathematical knowledge."

See also

digital library, List of encyclopedias