Sweet Blue Flowers is a schoolgirl lesbian romance by the mangaka of Wandering Son and is supposed to be very sweet and nonexploitative; available at Jmanga (and also a scanlation by one of the btter groups).

Rica 'tte Kanji!? is an autobiographical josei manga by a lesbian mangaka who comes out when she comes to the city for university, which came out in English from a small press, and is adorable.

Blue by Kiriko Nananan?

There is probably more, but I'm blanking on it. I have to admit most of the lesbian manga I have seen that doesn't make me cringe has been scanlated by Lililicious.