H2g2

h2g2 is a British-based collaborative online encyclopedia project engaged in the construction of, in its own words, "an unconventional guide to life, the universe, and everything", in the spirit of the fictional publication The Hitchhiker's Guide to the Galaxy from the science fiction comedy series of the same name by Douglas Adams. It was founded by Adams in 1999 and was run by the BBC between 2001 and 2011. It is often compared to Wikipedia but there are differences between the sites.

The intent was to create an Earth-focused guide that would allow members to share information about their geographic area and the local sites, activities and businesses, to help people decide where they want to go and what they may find when they get there. It has grown to contain subjects from restaurants and recipes, to quantum theory and history. Explicit advertising of businesses was forbidden when the site was run by the BBC, but customer reviews were permitted.

The content of the project is written by registered "Researchers" on its website. Articles written by Researchers form the "Guide" as a whole, with an "Edited Guide" being steadily created out of factual articles that have been peer reviewed via the aptly named "Peer Review". The Edited Guide includes both traditional encyclopaedic subjects and more idiosyncratic offerings, and while articles in the Edited Guide sometimes aim for a slightly humorous style, most are correct and well-written treatment of their subject matter by virtue of the Peer Review process. Every article has an associated discussion area which allows for multiple threads, called "Conversations".