On both Apple's dev forums and on the iphonedevsdk.com forums there have been several threads lately about the source code to a project called TouchFighter II. TouchFighter II is a game demo that Apple gave out at WWDC and is also, from what I've been told, giving it out at their iPhone tech Talks. It contains a lot of invaluable, reüsable objects that you can drop into your project and use. Although a few of the classes, like Texture2D, are available in other Sample Source projects, much of it is not.
The first thing I'm going to say is: get yourself a copy of this. If you went to WWDC, then go to the attendee site, log in and grab it. If you didn't, and you have an interest in writing iPhone games, then go to one of the Tech Talks that Apple gives. Even if you have to drive a few hours and take a day off of work, go. it would take you more than a day to write the functionality you will get for free from TouchFighter's code.
I have been asked by several people if I could send them a copy of the source code. I wish I could oblige, but the source code was given to us at WWDC under a blanket NDA. That NDA is not the NDA that was recently lifted by Apple, by the way, and is still very much in effect. You MUST get this source code directly from Apple. Do not ask other developers to provide you with a copy, as that puts them in a difficult position. Nobody likes to say no. I don't like to say no. This source code is invaluable, especially if you want to write an iPhone game, and I would love to see more developers able to benefit from it. But legally, I have to say no. If I were to give out the source code, I would risk losing my membership in the iPhone Developer Program. Considering that the iPhone is the basis of most of my income right now, that's not a risk I'm willing to take. Those of you who have asked me for the source code, please understand my situation and why I can't oblige, as much as I wish I could.
If you didn't go to WWDC and can't get to a Tech Talk, then open an enhancement request or call ADC to let them know you want them to make the TouchFighter II source code available in the iPhone Dev Center. If there is another way to get the source code besides the two I have mentioned, those are the people who can tell you.