Aiko-chan/SaraMichiru's site, it incorporates both animated and audio dramas.
Another page on aiko-chan/SaraMichiru's site, IMHO all WK fanfic authors should check this out at least once.
Summaries of Kapitel episodes
Yo-chan's site, has paragraph summaries of all the Kapitel episodes.
Not a complete list, but hey, who's complaining?
Jey Kama's site, Aya no Weiss kreuz Corner, has manga scans along with pics from them. Other info there, too.
And a reminder to keep it all in perspective
Smartania's Generally Sarcastic Guide to Anime: Weiss Kreuz