This is a great thread and very timely for me as well, as I am trying to expand my listening of more contemporary (living or at least mid/late 20th or 21st century) composers. A few that have been playing in my space recently:
Gabriela Lena Frank (first heard at Chicago Symphony), Alberto Ginastera, Per Nørgård, Mieczysław Weinberg, Henri Dutilleux, Stephen Hough, Rebecca Clarke, and Missy Mazzoli
I'll be checking out some of the others from this thread as well. Thanks for all of this.