???.. I use Gimp .. pretty good for image editing and creation, but for flyers and posters I use open office draw and others depending on need for text and whatnot.
There is even a version called "gimpshop" designed to be more familiar for photoshop users.
For an example of what can be done with free open source software (gimp is available for windows too).. see the back of my last CD .
Paula's great CD sleeve really does prove that you don't need Photoshop for many purposes. I'll stick with it because I have it and am used to it - and it is a first rate program. However, if I did not have access to Photoshop I'd certainly follow up the Gimp versions Paula mentions. In the end, it is often down to the facility and creativity of the operator rather than the program.
-Tony