If you’re remotely into photography, Google’s Picasa software will transform your life.
It organises your photos into easy-to-view files and has a basic yet comprehensive suite of really easy-to-use photo-editing tools, which will cover most of your editing needs. I can’t explain how much easier it is to use than Photoshop (which I still use for more tricky editing tasks).
Mostly I really hate software (which admittedly is a bit of a disadvantage if you’re running an online shop). It’s either full of bugs or has been designed by people whose brains work in strange and wondrously illogical ways, which means I spend a large part of my day engaged in software-cursing. Picasa, by contrast, is always helpful and almost cuddly.
It also has a rather sweet ‘collage’ tool.