Shrink-O-Matic is an application that works within the Adobe Air environment. You can use it to easily change the size of one or more images at a time.
It is quite intuitive to use: just drag and drop the images that you want to resize into the program interface, and it will register and resize them.
Shrink-O-Matic allows you to configure the output size of your images, their format, and their final quality.
Requires Adobe Air.