In my companies spare time we post code based on what we're doing for a client or another game development shop - currently that has been mostly cocos2d and unity3d. To that end, we created a site (
iphone game tutorials) that specifically tries to give back to a community that has been really good to us. Our latest tutorial is about tower defense games using cocos2d - this is really near and dear to me as I wrote a tutorial about it for flash that was very popular in 2006. I hope to do the same again for this game mechanic and hopefully get people past the initial hurdles for this very fun mechanic.
I would love to hear your thoughts - It's hard to put this sorta stuff out there for consumption to the masses, so I would appreciate only constructive feedback, please

Saying if it helped you out and spreading the word would be really nice as well

This is not our day job and we really are trying to give something back based on our experience at this point.
The tutorial links is here:
Part 1
Cocos2d Game Tutorial – How To Build a Tower Defense Game for the iPhone – Part 1 – Creep Waves!s
Part 2
Cocos2d Game Tutorial – How To Build a Tower Defense Game for the iPhone – Part 2 – Placing Towers.
Part 3, 4, 5 and 6
coming soon..
If you think tutorial topic that you would like written for a specific game mechanic, let us know and we'll be happy to do something. We have a few other game mechanics up already and hope to release more based on if people want them or not.
Thanks,
Walter
iPhone Game Tutorials