Different Folder Icons IconoMan
A package of over 130 free Metro-style icons for Windows system meets and exceeds the strict guidelines developed by Microsoft for operating system icons. The package contains 48x48 pixel images with a transparent background.
A collection of 711 PNG Windows Phone 7 icons for your WP7 applications. Every icon has the right size and color, meets Windows Phone 7 requirements and will help you save a good deal of time when designing a perfect UI!
Here is the iOS Icons bundle, which will help each iPhone or iPad application developer get his GUI look better. The icons from this icon set can be used in navigation, tab bars and toolbars of iOS applications.