So there’s a few ways so far to develop native apps for the iPhone. Let’s count the ways:
1. The Apple Way: These technologies are the native tools that Apple encourages developers to use. They include Objective-C, Cocoa, XCode and Interface Builder. You can find more information at the Apple Developer website.
2. The .NET Way: The Mono project’s version of the .NET framework. You can use C# and the .NET framework to make native apps. Check out MonoTouch for more information.
4. The Adobe Way: In Flash Professional CS5 (not out yet). You can use ActionScript to create Flash applications that will compile natively to the iPhone. Read more about it in Adobe’s FAQ.
The biggest downside is if you’re a Windows user, you’re mostly out of luck. Flash Professional CS5 is the only one so far that lets you develop on a Windows machine. The rest are for MacOS’s.