GIMP (GNU Image Manipulation Program) is a powerful image composition and
editing program, which can be extremely useful for creating logos and other
graphics for webpages. GIMP has many of the tools and filters you would expect
to find in similar commercial offerings, and some interesting extras as well.
GIMP provides a large image manipulation toolbox, including channel operations
and layers, effects, sub-pixel imaging and anti-aliasing, and conversions, all
with multi-level undo.