Image Smith is a batch image processor which you can use to crop, resize, rotate, invert, convert, and apply effects to a batch of images with ease. This application is available for both Macintosh and Windows.
Features
Resize
Supports many image formats
Change JPEG output quality
Flip Image
Change contrast, hue, saturation, and brightness levels
and more.
You can get this application worth $15.95 for free from here.
But I must say (at least for windows) IrfanView does almost all or more than this for free 
. See the features of IrfanView below
