Rename multiple files with change (very powerful), search/replace, insert, trim and many other batch operations. Features undo, preview, 'change'-operation and can work in sub directories on specified extension. Can also change name to ID3 v1 tags and modify files' ID3 tags which makes it perfect for renaming MP3's.

Renamer might not be the easiest program to use but it can automate some operations and work on several thousands of files, and might save you very much manual work.