1. Sumopaint – Online photo editing tool. Free for the basic version, but it has a pro version for less than $5/month. Your browser has to support Flash.
  2. GIMP – Best free alternative to Photoshop. Almost all the PS features are available in GIMP. Runs on all popular operating systems (Windows, Mac OS X, Linux).
  3. Paint.net – Much easier to use than Photoshop, but only runs on Windows. Not for professional use, but perfect for simple photo edits.
  4. Pixlr – Another browser based photo editing software, which uses Flash. Very easy to use, perfect for simple edits and no download is required! Pixlr is also available for smartphones.
  5. PixBuilder Studio – Photo editor for professional use. Looks similar to GIMP, but it has less features, so easier to use.