There are a few good desktop photo editors out there, some of which are free and other have the be purchased. However, the paradigm in technology is slowly sifting with the advent of Google Docs. More and more applications are online based making it easier for users to access them at any given time without administrator restrictions.
One useful applications have come to me attention regarding photo editing it's called SpalshUp. SplashUp is a powerful web application with great features, giving users - pros and novices - the ability to turn dull photos into masterpieces. Sharing these works of art can be done seemlessly using a flickr, facebook, picasa or splash account.
SplashUp has an interface that resembles that of Adobe's flag ship product, Photoshop. Users can use multiple layers and similar photoshop filters and tools (like the lasso, marquee, paint brush and many more).
All in all SmashUp, though in it's beta stage, is a wonderful application to have in a upcoming designers arsenal.