Here are the middle grade speculative fiction books from the bigger publishers that I know about that star young protagonists who aren't "white." Feel free to let me know about any I missed! And I'm keenly aware that defining "white" and making distinctions about who's diverse and who isn't is fraught as all get out, and is especially tricky when you're dealing with people who aren't from Earth, so please also feel free to disagree with me!
The links go to my own reviews, if I've reviewed the book, or to other places, if I haven't. I've put little stars (*) next to the books that were written by people who aren't white European types, in case anyone is looking for diverse authors, but goodness knows I have no idea about most of them.
Chitty Chitty Bang Bang and the Race Against Time, by Frank Cottrell Boyce (Candlewick)
The City of Death, by Sarwat Chadda (Scholastic)*
City of Death, by Laurence Yep (Starscape)*
The Creature Department, by Robert Paul Weston (Razorbill)
Darwen Arkwright and the School of Shadows, by A.J. Hartley (Razorbill)
Ghost Hawk, by Susan Cooper (Margaret K. McElderry Books)
The House of Hades, by Rick Riordan (Disney-Hyperion)
How I Became a Ghost, by Tim Tingle (The Road Runner Press)*
The Infinity Ring series (books 3-6 were published in 2013), various authors (Scholastic) *(for Matt de la Pena).
Jacob Wonderbar and the Intersellar Time Warp, by Nathan Bransford (Dial)
Jinx, by Sage Blackwood (Katherine Tegen Books)
Killer Species-- Menace From the Deep, and Feeding Frenzy, by Michael P. Spradlin
Leopards' Gold (Chronicles of the Red King Book 3) by Jenny Nimmo (Scholastic)
The Menagerie, by Tui T. Sutherland and Kari Sutherland (Harper Collins)
The Monster in the Mudball, by S.P. Gates (Tu Books)
My Neighbor Totoro, by Tsugiko Kubo (Viz Media)*
Paradox by A.J. Paquette (Random House)
Parched, by Melanie Crowder (HMH Books for Young Readers)
The Real Boy, by Anne Ursu (Walden Pond Press)
The Time Fetch, by Amy Herrick (Algonquin Young Readers)
The Unmaking, by Catherine Egan (Coteau Books)
The Water Castle, by Megan Frazer Blakemore (Walker Childrens)
The Wells Bequest, by Polly Shulman (Nancy Paulsen Books)
Wild Born (Spirit Animals Book 1) by Brandon Mull (Scholastic)
Zombie Baseball Beatdown, by Paolo Bacigalupi (Little Brown)
There are of course lots independently published books that star characters of color; here are two I know about because they were nominated for the Cybils:
The Adventures of Emery Jones, Boy Science Wonder: Bending Time, by Charles Johnson and Elisheba Johnson (Booktrope Editions)*
Song of the Mountain, by Michelle Isenhoff (CreateSpace)
That's 31 books, which is better than some years, but still a pretty small percentage of the total (which I feel I can say with confidence despite having No Idea how many middle grade speculative fiction books are published in a given year).
This is also the first list I've made that includes a middle grade speculative fiction book written by a Native American author (Tim Tingle). It also includes the first middle grade dystopia set in a future Africa book I know of (Parched).
There's no point, I think, in seeing which publisher publishes the most, because some, like Scholastic and HarperCollins, publish more MG Spec Fic than others, so the odds are on their sides.
In any event, there they are, and may many more come in 2014!