Platform: Windows XP, Windows Vista
Number of downloads: 12579
Irfanview is a great utility for opening and saving in a vast range of graphics file formats as well as performing a reasonable amount of manipulation along the way.
It's designed for situations where the Windows Paint program just fails to cut the mustard.
Effects include blur, emboss, oil paint, edge detection, explosion and pixellise, while the enhance colours option allows you to adjust red, green and blue levels along with brightness and contrast. There are sharpening and resolution adjustments too.
Some of the most obscure formats - such as those native to Sun and SGI (Silicon Graphics) platforms, along with bitmaps for mobiles - require additional plug-ins but these, too, are free downloads.
This latest 4.x adds support for a new paint plugin, support for previewing FLV files, new effects and much more.