If you love modifying photos, can’t afford Photoshop, and don’t think MS Paint is up to the task, try The GIMP.  If you have used it before, you’ll be glad to hear version 2.4 is out.  Newsforge has a breakdown of what’s new and improved.
A major update to the GNU Image Manipulation Program (GIMP), widely regarded as the leading free software raster image editing program, is scheduled for this month. The 2.4 release is expected to include a number of new features and enhancements to existing features.