Here are some Photoshop alternatives you might want to try:
Paint.NET (Windows + Mac + Linux)
GIMP (All OS)
GIMPSHOP (ALL OS)
XARA XTREME (Free version only for Linux users)
Ultimate Paint (free version) (Win)
Pixia(Win)
Serif DrawPlus (Win)
ArtRage
ImageForge
Artweaver
Inkscape (Linux + Windows + Mac)
Sodipodi
Karbon14 (for linux users running under the KDE desktop env.)
ZonerDraw
Sketsa SVG Editor
If you have more worth a look post them down here.