Easy Image Modifier is a batch processing tool that will quickly resize, rename or otherwise process the images you specify.
You can have the program carry out simple rotations, for instance (90 and 180 degrees, flip horizontally or vertically).
There are options to resize your images, either to a fixed size (800 x 600) or as a percentage of the original.
Easy Image Modifier can convert file formats from or to JPG, PNG or BMP. It can rename your files, according to a pattern that you define. The Settings dialog has assorted further tweaks that you make: resizing can be proportionally or not, JPG's can optionally remove metadata, and so on.
And once you've defined the actions you'd like to perform, simply drag and drop your images onto the program, click a button, and they'll be converted to suit your requirements.