Modern UI Icons (also named Windows Phone Icon Pack) is a set of 750+ very beautifully designed icons.
The icons are created with Windows Phone and Windows 8 developers in mind, however, they can fit very well to any web/mobile/desktop project.
This set was featured at WRD before when there was ~140 icons but it has grew so much, moved into a new domain and deserves a 2nd shot.
They are designed with Expression Design and comes with 48*48px PNG (light and dark), .design and .XAML versions.
It includes many items from actions to filetypes, weather, charts and much more.