MSDN hosts a number of excellent blogs including the .NET Framework Blog. They are not exclusively .NET:
In VS2013 RTM we introduced the Performance and Diagnostics hub with a bunch of tools that help you diagnose issues during your Windows Store app development. With VS2013 Update 2 we added two brand new tools: CPU Usage, and Memory Usage. We also made all the tools in the Performance Diagnostics hub applicable to Windows Phone 8.1 development.
It’s also worth highlighting here the addition of the JSON Debugger Visualizer to Update 2.
Check it out. And check out other developer tools blogs on MSDN.