Core-Renamer is a tool for conveniently renaming a set of files. It is written for Mac OS 10.6 but should run on Mac OS 10.5 as well.

Features:

Apply several renaming steps in a row before you actually rename the files
Reorder the files as you like (e.g. for numbering) or click on the columns for automatic ordering
Drag & drop files into the table
Unlimited undo / redo
Replace a string with another string
Delete a given amount of characters either from the beginning, from the end or in a certain range
Insert a string at a given location
Change the character case
Number the files with a specified delimiter