Just few clicks and you're done.
Do not waste your time on resizing, renaming and converting of each icon, better save it for more important things.
QuickIcons is quite an easy to use app that can convert common image formats to icons for
- iOS (inclusive iOS7 resolution png-files)
- Mac OS X (.icns and iconset)
- Android (ldpi, mdpi, hdpi, xhdpi, xxhdpi resolutions)
- Windows (.ico and bmp-files)
- Windows Phone (png-files)
- BlackBerry (png-files)
With possibility to enable and disable the icons creation for the particular platforms.

Enjoy it!