Gimp (GNU Image Manipulation Program), THE Linux image editing program is on its way to a version 2.0. A beta version is now available for testing (2pre1). For those of you with Mac OS X, you can run Gimp through X11.
http://openosx.com has a beautiful full screen image of it running in OS X here
You can see the layout is starting to resemble Photoshop more, and to me, the tool icons seem very MM Studio MX 2004.