GIMP: An open source photo editor

An alternative to Photoshop
So, you want the power of high-end image editing programs like Adobe Photoshop (or Corel PaintShop Pro) but have zero money to spend. The GNU Image Manipulation Program (a.k.a. The GIMP) gives you professional-level image editing capabilities at a budget price. It's free! And it's available for Windows, Mac, and Linux. Find out more at the GIMP website. The Mac GIMP version runs on the UNIX sublayer of MacOS and requires X11 (a version of Xwindows) which may be a deal breaker for all but the Geekiest of Mac users (not your typical Mac user can work in X11). Supposedly, the Windows version is not so constrained and would be easier on the casual user. There are tutorials to using GIMP on their Website and elsewhere on the Internet.