Flixel is a great open-source game making library. The ActionScript library can be found here. This template is for the Objective-C library that was used to make Canabalt.
If you are using Xcode 3, move all of the files within the Xcode3 directory to Developers/Platforms/iPhoneOS.platform/Developer/Library/Xcode/Project\ Templates/Application.
For Xcode 4, drag all of the files within the Xcode4 directory to ~/Library/Developer/Xcode/Templates.
Base templates taken from the Cocos2D templates.