This is a free 3D game multi-physics library that is used in some of the popular games released on the App Store.
Joe Hewitt’s Three20 Open-Source Objective-C library
Three20 is a complete set of iPhone UI classes. It includes things a photo viewer and also general utilities like the HTTP disk cache. It has been derived from the famous Facebook iPhone app – which is the number one downloaded app on the App store.
This is a framework for building 2D games for the iPhone and the iPod Touch. It has a very supporting community, and is completely open-source engine. This is a must get for all aspiring iPhone game developers.
Matt Legend Gemmell – Cocoa Source Code
Matt Gemmell has put out some of the greatest code out there for the iPhone developer community. You have probably heard of his stuff including MGTwitterEngine, the Twitter API used in iPhone apps Birdhouse and Twitteriffic.
This is a blog that is an open-source collection of 31 mini-iPhone app projects to help you polish up your skills quickly.?