Have you ever discovered the perfect icon set, only to find it wasn't available for your particular platform? iConvert solves the problem: With this free online icon converter, you can convert any icon or image into an icon specifically for your platform. iConvert allows you to easily convert PNG to ICO, Windows ico to Mac OS X icns, SVG icons to Windows icons, PNG icons to Mac OS X icons, JPG to ICO, and much more. Simply upload a file in one of the supported formats, and iConvert will do the rest!

This does allow you to create multi-level icons. There are also apps available for Mac and Windows for £3.12 which is awesome if you are going to use it a lot. The online version of this software is great for most of us for the occasional use.

You can use a url or upload an image for the conversion.