Interesting Mobile 5.0 APIs are being released - you'll get them in ROM and hence do not have to be deployed to the target by your setup programs. To code against them, you need to download the free Windows Mobile 5.0 SDK which installs the six libraries that you can reference from your Visual Studio 2005 Smart Device project, so you can use the namespaces and types and gain access to the new features. The SDK also provides Windows Mobile 5.0 emulators for use from within Visual Studio 2005. These class libraries are (in no particular order):
Now that your appetite is whetted, browse the online documentation for more details and install the Windows Mobile 5.0 SDK to have a play in your favourite language (C# or Visual Basic):