Por ahora en Ingles, luego lo traduzco:
Sizerox is an application that resizes your “JPEG”, “TIFF”, “PNG” or “PSD” images and saves them as “JPEG”. You can easily resize, rename, crop, rotate and watermark your images from your digital camera or scanner to send them with e-mails, to use them on the web or to upload them to your iPod
EasyCrop is a small application that crops and resizes images, has a live preview, supports drag and drop and has built-in screen capture tool
EasyBatchPhoto frees you from repetitive tasks of converting, resizing and watermarking images by processing hundreds, or even thousands, of images with a single drag-and-drop.
iResize – Batch resize and compress images in .jpeg, .pict, .tiff,.gif, .psd formats.
SmallImage is a simple and efficient tool to batch process JPEG files, resize them, recompress them, remove embedded profiles and make them ready for the web or store them efficiently.
Then there are other options, such as Apple scripts that let you resize images by just dragging and dropping images onto a script icon (on Mac OSX Hints) or even Automator actions, one of which is Resize Pictures Suite.
Fuente: http://www.silvermac.com/2007/resizing-images-in-mac-os-x/