Not sure how we missed this, but some time ago Publisher's Weekly (PW) had a great roundup of some new and interesting YA publishers and imprints:
"Looking beyond the houses responsible for many of the bold-faced headliners at the top of bestseller lists, one finds an enthusiastic group of publishers, some newcomers to YA. . . . Here's a look at some of these publishers' offerings and observations."
If you write for young adults, you'll want to read the full article, Today's YA Scene: New Players, Innovative Directions, Fresh Voices, and perhaps even add a few of them to your next submission list!