Novell offers iPhone .Net app development kit.
This is all based on the open source Mono Project, which enables Microsoft .Net applications to run on Linux, Unix, and the Macintosh, and now the iPhone. And with Mono, developers can run binaries produced by Visual Studio on other platforms. There's even a Mono Migration Analysis tool to check if everything that an application uses has been implemented in Mono or if there are special considerations to keep in mind. This should mean that more applications, written in .NET or C#, can migrate to the iPhone. Supposedly developers can take advantage of native iPhon3 APIs, while a cross-compiler turns .Net executables into native iPhone apps.
Monotouch is integrated with Apple's IDE so that developers can test their apps on the iPhone simulator. Bottomline: developers that don't know Objective-C but have programmed in .NET or C# can now use their skills to create iPhone apps. There's even a "Hello World" app available that can get you started at the Monotouch Tutorials page. For more information visit the Monotouch website.