I'm kind of disappointed that Card keeps writing books based on Battle School among other things outside the five original Ender novels
I also haven't read anything past Speaker for the Dead, since the end of that novel was very obviously a set up for the next one, and I liked Speaker for the Dead too much to come to expect the same thing form the later novels.
You haven't read the whole Ender Quintet, so you wouldn't know why and I won't say because spoilers, but Ender's story comes to a very absolute conclusion in Children of the Mind. If you don't care about spoilers,
Ender dies.
There's a bunch of characters that Children of the Mind gave us though that have lingering plot threads and need to be tied up. That's supposed to happen in a book titled Shadows Alive, and is also supposed to bring together the story from the Shadow Saga and the Ender Quintet. This book was announced a long time ago though and nothing has happened with it.
There's so many books I can't keep track.
Here's a simple run down of all the books:
Ender Quintet: Ender's Game, Speaker for the Dead, Xenocide, Children of the Mind
Shadow Saga: Ender's Shadow, Shadow of the Hegemon, Shadow Puppets, Shadow of the Giant
The Ender Quintet and the Shadow Saga are the main books of the series. The Ender Quintet tells the story of Ender. The Shadow Saga tells the story of Bean. The Shadow Saga also acts as a setup for quite a few of the plot points that appear in the Quintet, though not very directly.
First Meeting: This book is not actually a book. It's a collection of side stories. One story is about Ender's dad, John Paul. Another story is about how John Paul and how he meets Theresa, the woman who becomes Ender's mother. The third story is the original short story that was Ender's Game and is non-canon. The final story is about Ender meeting Jane and is probably the only worthwhile story in the book.
A War of Gift: A short story that takes place during Ender's time in Battle School. It's about a boy named Zeck. It's not related to the rest of the series in anyway though.
Ender in Exile: An interquel between Ender's Game and Speaker for the Dead and is actually about Ender. It follows his story on the ship that he and Valentine are traveling on to go to the first colony. And then actually the story of them being at the colony. And then after they leave the colony. It also ties in with the Shadow Saga and solves a big mystery that was left in those books. Probably the best book that's not apart of the main sagas.
Shadows in Flight: A sequel to the Shadow Saga that is about Bean and his children. They discover some really interesting Formic stuff. Introduces some things about Hive Queens that makes you question a lot of what happens in the Ender Quintet
that may or may not mean she is actually a villain.
Formic Wars trilogy: Earth Unaware, Earth Afire
The Formic Wars trilogy is the newest books. The final book, Earth Awakens, is coming out in 2014. This trilogy is about the first Formic War. The first book, Earth Unaware, was pretty good. I haven't read Earth Afire all the way through yet, but I read about half of it and didn't care for a lot of it.