I have researched and written extensively on fandom history in particular. You can look more into this on my list of created pages on Fanlore and read only the results of my research on my Dreamwidth journal.
I have a growing database of archived dissociative, multiple, and plural sites. Somewhat similar is an extensive list of mentions of asexuality predating the year 2000.
Also available are collections and lists of old, typically offline, fanfiction in a variety of fandoms, which are listed here. Other important media archives (to which you can contribute!) are listed here.
I also host a small Newsies fanfiction archive, to which anyone can submit their own fanworks (including works which are not fanfiction)! It can be found here!