Gimp is an alternative software to Photoshop. Most users of linux use Gimp instead of Photoshop. Last version of Gimp is 2.8. I use it myself in my ubuntu 11.10 Oneiric Ocelot and Linux Mint 1.14 Nadia.
I recommend it to you if you are using a distiribution of linux. If you are using Windows or other platforms, I think Photoshop is...