BiggieSmall is a simple application that allows you to resize multiple photos in a snap. You just need to load the photos you wish to resize, choose the scaling type and click "Export". The resized images can be overwritten, you can always save them in a specific folder, or you can be asked where you wish to save them every time you export new files.
The application includes several scaling options that include Fit into (you select the desired width and height), Max width and height (you select the maximum values), Percentage (you select the compression percentage), and None. Moreover, for all the scaling options you can select the format (JPG, JPG2000, PNG, TIFF, or BMP) and the image quality. The program also includes a view option, which allows you to zoom in any of the selected images. In the trial version you will be able to use the program with no limitation, but the converted images will show a big watermark with the name of the program.
In short, if you are looking for a simple and easy to use image resizer, BiggieSmall may be useful for you.