Photoshop CS2 Free
The 2005 version of Photoshop suite (including Illustrator) has just gone free-to-use on Adobe's site. The evil empire did something right!
It works great on any Windows PC and any Snow Leopard or PowerPC Mac. (Lion & Mountain Lion removed PPC app support.)
Adobe's site is slammed right now, but you can read about the offer here and grab it when things slow down: