This page contains descriptions and a few teaser scans of yuri scenes from various manga and doujinshi; it also contains various yuri- and Maria-sama ga Miteru-related files, which can be found here. Feel free to pimp the server as much as you'd like. :)
Most of the descriptions were originally written for the daily_yuri community on livejournal, but I wanted to share them with a broader audience.
A note on the scans: I found most of these scans using the Japanese peer-to-peer programs Winny and Share. It should go without saying that they're free-use, although I don't believe in "ownership" of scans anyway. It would be nice if you could mention the title and mangaka when posting the scans other places, though, so that people know what they're from. :)
I've included the ISBNs for all of the manga (save the ones that are only available printed in magazines); I believe none of them are out of print yet, so you should be able to get them through most Japanese bookstores.
At this time, none of the scans posted here will contain adult content, even if they come from H-manga.
One last warning: these descriptions contain spoilers. Read at your own risk.
10/3/2008: Dystopia added.
10/6/2008: See here if you would like to request a doujinshi scan (NOT a translation) from the list of titles I have.
4/3/2008: Utena and another Yuri Tengoku 2 story added.
Anata to Scandal volume 3
Beauty and the Beast (Sailor Moon doujinshi)
Discommunication chapter 82
Futtemo Haretemo (Come Rain or Come Shine)
Gamen no Kokuhaku
Goshujin-sama ni Amai Ringo no Okashi
Hanakotoba (Flower Language)
Hansel, Gretel, and the Witch
Hoshi ni Negai wo (Sailor Moon doujinshi)
Kami Naki Tsukiyo no Gensoukyoku (Kannazuki no Miko doujinshi)
Kashimashi ~Girl Meets Girl~
Killer Queen (Maria-sama ga Miteru doujinshi)
Koucha Ouji volume 11 sidestory
Lavender of Romance 6
Little Yuri Riding Hood
The Little Mermaid
Maria-sama ga Miteru: Answer (text translation)
Maria-sama ga Miteru: White Petals (text translation)
Nikurashii Anata e
The Red Demon Who Cried "Moe!"
Saigo no Seifuku
Saint Mary (Maria-sama ga Miteru doujinshi)
Sakura no Kiwa
Shi ga Futari wo Wakatsu Made (Sailor Moon doujinshi)
Shoujo no Kisetsu
Sweet & Bitter
Tou no Naka no Himegimi (Sailor Moon doujinshi)
Transistor ni Venus
Utena (Utena doujinshi)
The Wolf-Girl and the Seven Kids
Yubisaki Milk Tea
Yuri Tengoku 2