From Halopedia, the Halo wiki
Halopedia Archives are Archives related to Halopedia itself.
Letters of Canon
Letters of Canon were letters that Halopedia and its fans sent directly to Bungie, 343 Industries or other official sources to determine specifics of canon. These letters for the most part are impossible to verify if they are real, and thusly can not be used as official canon. Many letters have also not been followed as later media have been released. They are recorded here for posterity, so if required we can look back on them.
Canon Debates/Request for Move
Canon Debates/Requests for Move were old discussions on several topics on Halo. Prior to July 2010 they were used to help the wiki decide on how to deal with certain articles. To discuss these topics nowadays visit the Halopedia forums here.
The Halo Nation archive is a set of content related to the Halopedia/Halo Nation merger. This set of stuff will be merged into the relevant articles when the time is relevant.
This is a list of stuff that does not particularly link up with any of the sections above.