The UESP (or Unofficial Elder Scrolls Pages) is one of the largest and longest-lived fanmade websites out there. It's had a presence on the net since 1995, and switched to a collaborative wiki format in 2005. As an editor, my contributions to the site include documenting all twelve video games and related books, maintaining a high level of quality, providing images, adding deep technical knowledge of the games, and writing extensively on the series' fantasy setting. As an administrator, I've contributed to shaping site policies, handled everything from vandals to in-house disputes, managed copyright licenses on hosted third party files, and acted as an in-game community leader.
My contributions to the site can be viewed here.