With our DS7, we had him start his own blog about his favorite topic, Minecraft. He doesn't write on it as much as I'd like, but with encouragement, he will write about exciting new releases of the game and what he's working on. We used a free wordpress blog.

I welcome other sneaky ideas too...Mine DS skipped 1st (which apparently was a big writing practice year), and he has always hated writing (mechanics and handwriting both).