LongHorn SDK Preview Site
Generating a fair amount of controversy on its message boards, Microsoft's future OS version promises to be an even more radical step than (say) the migration from VB to VB.NET. A new version of the Windows API (WinFX, all in Managed Code), a new graphics engine (Avalon, with a declarative XML-based programming syntax, XAML) and a new file system (WinFS) mean plenty to think about. Of course, you may be required to sell your family into slavery before you will get a licence to run anything under the proposed "Trustworthy Computing" scheme, but such is life. And "Avalon" was a rubbish song. Anyway, this site provides previews of the SDK for some of the features and programming concepts, and for such an early stage it looks promising.