In Azure, there's no direct access to the operating system or the software running on top of it—it's some kind of Windows variant, optimized for scalability, running some kind of IIS-like Web server with a .NET runtime—but with far fewer restrictions on application development than in Google's environment. Though .NET is, unsurprisingly, the preferred development platform, applications can be written using PHP, Java, or native code if preferred.
Introduction to Windows Azure, cloud service from Microsoft, including comparison with Amazon Web Services and Google App Engine.