Lauren Jankowski is a sister member of Broad Universe. I first met her at WisCon. She's an indie author who also runs a Tumblr called Asexual Artists. You can learn more about her on her website and find her books on Amazon.
N.K. Jemsin was a guest of Honor at WisCon last year. I must shamefully admit I missed her speech. (I think we were visiting college friends that evening.) However, I have read her Inheritance Trilogy and recommend it. Considering her first book, The Hundred Thousand Kingdoms, was nominated for a Hugo, Nebula, World Fantasy, and Tiptree Award, I think a lot of other people enjoyed it too. Learn more about Jemsin on her website, Wikipedia, and Amazon.
I'm most familiar with Kij Johnson's novels The Fox Woman and Fudoki, but she's written a lot of short stories, some of them award-winning. You can find her full bibliography on her website or Wikipedia, and her books are of course on Amazon.
The only book of Gwyneth Jones' that I've read is Life, but the story of the woman scientist in that novel really resonated with me. Jones has written many books in her career and has won, among other awards, the the World Fantasy Award and the Tiptree. You can learn more about her and her works on her blog, Wikipedia, and Amazon.
What other SF/fantasy women authors would you add to the J section? Please list them below.