Renamer4Mac is an advanced file renaming tool for Mac OS.
Where was this app just a few weeks ago? I needed this desperately and ended up bugging my programmer for 30 minutes as we wrote a shell script (never done that before) to make some pretty sophisticated file-renames. However, I was pretty nervous to hit “go” in case I missed something… Now, here this is with live previewing, so you can see exactly how your files will be renamed before you hit Go.
Renamer4Mac supports Regular Expressions (yay! regex), search and replace, insert/overwrite of text, numbering files, and capitalization. Whew. It’s also donationware, so make sure you support these guys if you like their work.