Paint.net

maroush, Photoshop is in a class of its own, but GIMP and Paint.NET are programs you'd expect to use for image manipulation if you don't need the bells and whistles of a specialized paid-for program like photoshop.

I've used both GIMP and Paint.NET, and slightly prefer the latter because of it's ease of use. Both have pretty much the same functionality, but Paint.NET is sleeker and cleaner interface, tools and widgets are more intuitive, and the secondary image windows aren't as bulky as they are in GIMP.