There aren't many true yuri anime around. My list has more yuri as a sideline but better some than none ^^ You can wiki it before watching just to see what its about and if you think you'll like it.
Bakuretsu Tenshi (awesome even without the yuri)
Blue Drop
Candy Boy
Madlax
Simoun (highly recommend this one)
Ga-rei zero
The whole Mai series (good anime even without yuri)
Aoi Hana (has yuri as main)
Maria-sama ga Miteru
Kannaduki No miko
Kyoushiro To Towa No Sora (has kannaduki main character on the sidelines)
Yami to Boushi to Hon no Tabibito
Shoujo-sect (its close to hentai but i like the story line)
Ikkitousen Trilogy
He is my Master
Utena + Movie
Strawberry Panic
Ikkitousen Trilogy
Hope it helps. ^^
