With Windows 8 now formally launched, it's time to get your hands dirty working on it.
A number of extensions and toolkits have been built and released on various sites to enable developers achieve better productivity and faster development. Here are some of them:
Callisto: A toolkit for XAML Windows 8 Store apps
Built by Tim Heuer, it is a toolkit of sorts for XAML-based Windows 8 Store apps. He started it during the Consumer Preview and has put it up on github.
https://github.com/timheuer/callisto
WinRT XAML Toolkit
The Windows Runtime (WinRT) XAML Toolkit can be found at Codeplex and contains a number of controls and helpers that help you build Windows 8 Store applications.
http://winrtxamltoolkit.codeplex.com/
Windows Azure Toolkit for Windows 8
This toolkit makes it easy to build a cloud service to support rich Windows Store apps. It has all the tools to enable easier development of a Windows Azure service and deploy it to users. The toolkit includes Visual Studio project templates for a sample Windows Store app and a Windows Azure cloud project.
http://watwindows8.codeplex.com/
Windows 8 apps: Multilingual App Toolkit
This toolkit is an extension for Visual Studio 2012 helps you localize your Windows app with translation support, translation file management, and editor tools.