I lack knowledge about yuri but I frequent 4chan's /y/ board so yaoi's my thing.
From my own experience I could recommend these yaoi mangas:
Three Wolves Mountain, Love Neco, Cute Beast, Petto Oshigotochuu, Sugarmilk, The Circle, Toraware no Mi, Hada no Ue no Renai Jijou, Loup-Garou Gokou, Inu mo Arukeba Fallin' Love, Wild Rock, Yuuwaku Sentiment and Zion no Koeda.
And I highly recommend checking out Naono Bohra's stuff. She's an amazing artist and althought it's pretty much censored like everything in Japan (STOOPID CLOUDS), it's more graphic than many others I've read.