h2g2 is an Everything-like system inspired by and named after Douglas Adams' Hitch Hiker's Guide to the Galaxy. Launched in April 1999, it became absorbed into the BBC in February 2001. The idea is fundamentally the same as Everything2, with some differences such as allowing external links, different writetups with the same title being displayed on different pages, etc...
Oh, and it also has smiley images. Ahem.
See also The Difference between Everything2 and H2G2.
You can go and judge for yourself at http://www.bbc.co.uk/h2g2/.
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