One of the most annoying things about downloading photos from a camera is that all of the filenames are given generic titles like "pic001.jpg".
This can soon lead to confusion if you're downloading several batches of photos or photo from different camera. ExifRenamer is a tool to help you rename all of your digital photos in a few clicks using a more logical date and time format (i.e. YYYY-MM-DD / hh-mm-ss), so you can at least more easily sort and organize photos chronologically.
ExifRenamer allows you to preview photos and add a prefix or suffix to the date format for even easier identification. Importantly, it supports batch changes meaning you can upload an unlimited number of photos to be changed at once. If you use Apple's ImageCapture for retrieving your photos from a camera, it can even automatically rename downloaded pictures saving you a lot of time and hassle and now this function supports Snow Leopard too.
ExifRenamer is an excellent tool for renaming your batches of photos.