If you've ever imported a couple hundred photos from your camera, you know the most common file names a camera uses are essentially meaningless. If you want a quick and easy way to find and replace specific parts of a file name, FreshBatch is a lightweight tool that does just that.
FreshBatch works essentially like a find and replace option, where it only replaces the keyword you list, but retains everything else. It's great for quickly renaming a bunch of files you've just imported or downloaded. It doesn't have a lot of options, but that's part of the appeal. It's simple, lightweight and makes bulk file changes a painless process. It's also able to swap extensions, which is handy if your camera has the tendency to upload in all caps. FreshBatch is a free download from the developers site below.