http://www.les-stooges.org/pascal/pencil/index.php?id=Home people have asked about this many times, and this is what i use. it's free. seashore / gimp are photoshop clones and are, in their own ways not ideal. seashore lacks features and gimp's interface is very much not OSX, runs in X11, etc. i have pixelmator which gets better with each update and will hopefully someday be able to really compete with photoshop.