iPhoners have their Words with Friends. Do we have any turn based games? With this community, I know I have people to play against.
Check our Alpha Jax sticky at the top of this forum I think that has you covered. Those guys will even play with you if you want.
Are there any other turn based XBL games in the market, besides Alpha Jax? Do we even have games that we can play between Xbox and WP yet?
Besides Words By Post I can't think of any off the top of my head other then one that I'm in a beta for (up to 3 players turn based). AS for Xbox and WP nothing announced yet but hopefully we'll see movement on that front sooner then later.
Microsoft has a multiplayer chess game, Game Chest: Logic Games. I started a game on Xbox.com and it seems to have carried over to the phone version of Game Chest. It even shows up in the requests section of the Xbox Games hub.