These are links to websites I know of which include Eroica-related material. If you know of an additional site which could be included in this list please let me know.

Aoike's official site, in Japanese.

Fanfic, links to online Eroica resources, a fact sheet, and other info.

A LiveJournal community for discussion related to Eroica and other Aoike works.

A LiveJournal community for Eroica fan fiction.

Material from the site formerly at eroica.nu, including a fanfic archive, fan art, and assorted other items.

A list of suggestions for actors to play various Eroica characters in a hypothetical film version. This is purely a fantasy casting game, so there are no time constraints -- actors from many periods are listed.

A Japanese site, this one is the online base for a long-running (since 1978) Japanese fan club devoted to Major Eberbach. Though most of the site is in Japanese, it does have some pages now available in English.

Not about Eroica per se, but a very interesting site on shoujo manga fandom in Japan. This is an English-language site maintained by an anthropologist who is doing his dissertation on the subject.