The GIMP (GNU Image Manipulation Program) is an easy-to-use freeware program that may not make image editing a snap, but the learning curve is pretty gentle and there's lots of help available.

The program can import/export into just about any file you can imagine (except proprietary formats Like the ones Adobe uses).

Image resizing and scaling is easy(ish). Right clicking will bring up a menu that allows you to do pretty much anything with your image, including scaling it to the size of the selection or cutting and cropping.

Screenshot of the main editing window, with my most excellent steampunk desktop in the background.

I'd reccomend a paid program for a professional who needs a heavy-duty vector image producer, but GIMP is just fine for home users. And it's free, which is a major bonus.