Like Graphic Converter for the Mac, Irfanview is invaluable for converting picture files to a wide range of formats. There are many more besides the usual web and cellphone standards of GIF and JPEG.

If you're sending photos by email or mobile messaging, you can convert your pictures when needed to a format your recipient can view. At the same time you can optimize your images - free - in Irfanview to reduce your file size and cost. (And these days this is often necessary. Multi-megabyte mobile messaging, for instance, direct from one of the new megapixel camera phones, can get pretty pricey!)

If you fancy putting pen to paper (or stylus to tablet) and drawing a favicon that shows at several sizes, you can convert it in Irfanview to an .ICO file that displays a special picture for each location it's shown. You do get a better display when each size has its own picture, though this is not strictly necessary for a favicon.

Irfanview offers many more tricks, and it won't cost you anything.

Below are some other tried-and-tested art editors. All can be used for making or editing very tiny pictures for mobile phones or the web. MS Paint like Irfanview is free (MSpaint probably came with your PC).

Photoshop (or its little brother Photoshop Elements, astonishingly powerful yet a fraction of the cost of the full Photoshop,) can be used on Macs or PCs.

IrfanView, free image converter and optimizer