iPhoto came bundled with every Mac I've bought since 2002, very handy tool for photo correction and resizing and the book publishing feature is a nice plus. I use Image Ready from Adobe for resizing and the ubiquitous Photoshop (CS) for image adjustment. I used GIMP years ago on a Linux machine I built and I have to admit it's well thought out and worked; it's my understanding that it is now cross-platform friendly but I haven't given it a try.
