Are there any expansion boards out there that use the kinetis specific I/O pins ?
AFIK there is no dedicated document for this, and now standard. Every board has different pins on the inner rows. The best document for it is is the schematics PDF.
not sure what you mean with Kinetis specific I/O pins? Or do you mean the inner rows? They make sense if you develop your own board. I'm not aware of any commercial boards which use them. The outer 'standard' rows can be used with all the 'Arduino' shields as long they are designed to work with 3.3V logic levels.
I hope this helps,