Free Logo Creation Software

What free software can be used for logos or specific model?

I want to start my own shirts and screen printing, possibly posters, but I want to design my own creation. So I need software to allow me to change or add details of my pictures, I scanned the computer? Suggestions? It must be free, but must be at a reasonable price.

Gimpshop is a free / open the image editing program source code

Easy Banner Creator. Make Free Flash Web Logo Design Ad Generator Animated Maker Software