Below are links to some of the websites that I, personally, use quite often and enjoy visiting.

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General Information

Hitoshi Doi's Sailor Moon Encyclopedia GREAT episode summaries for all 200 episodes
Bishoujo Senshi Sailormoon Anime & Manga everything you need to know about the manga

Image Galleries

Serenitatis the IT page for images, everything you could ever want in both anime and manga
Sailor Moon Manga Utopia a smaller gallery with nice manga images

Fanfiction

A Sailor Moon Romance the original and greatest Sailor Moon fanfiction archive on the net
First Love Fics a large 1st season romance archive that is run by the wonderful author Alicia Blade
Moonlit Eclipse an archive that houses the amazing Aimee & Angela's work, HIGHLY recommended
Moonlight Mirage a smaller archive with some great Inuyasha fanfics as well
Fanfiction.net the new thing in fanfiction with any and every fandom you could ever want