Métamorphose File -n- Folder Renamer is a free, open source mass renaming program that combines great flexability with an intuitive interface.
Allows many command line renaming operations in a single utility, perfect for those of us that need to rename large numbers of files and/or folders on a regular basis. However, the ease of the interface ensures a one-time user (I need to rename 5 gigs of mp3´s) will not find it too frustrating to use.

Main Features:

• Renames files and folders at the same time.
• Preview every item to be renamed before comiting changes.
• Load all files in directory and in subdirectories (recursive renaming).
• Undo renaming operation in case of mistakes.
• Save all program settings to file for later use!
• Multi-language support, French and Spanish translations.
• Renaming operations:
  1. Prefix
  2. Suffix
  3. Set file extension.
  4. Replacement or modification by: Character, position, or regular expression.
  5. Insertion by: Position or every (number) characters.
  6. Length modifications (padding, truncating, or both).
• Renaming styles: combination of: user text, numbering, id3 tags, date, time.
• Modifications: UPPERCASE, lowercase, Capitalize first, Title Style, sWAP cASE, ´DoRkIfY´
• Sequential numbering (enumerating) options:
  
  1. Use integers, alphabetical, or roman numerals
  2. Pad with any valid character to any width.(integers only)
  3. Control step size, starting number, reset count.
• Rename MP3 files according to their ID3 tags.
• Set date and time manually or get from system.
• Use supplied defaults or specify your own date and time formats.
• Modular design allows great flexability and control, while keeping the easy stuff simple.

Please visit the home page for more info, and to download Métamorphose for other platforms (Linux, BSD, OSX)

What's New in version 0.5.0 Beta:

• Fixed: Config file issues.
• Fixed: Exif tag processing bugs.
• Fixed: Id3 tag retrieval.
• Fixed: Allow setting directory placement when sorting by stat.
• Fixed: Missing dll files in WIndows Installer.
• Fixed: Preference issues under Windows.
• Added: Command line options processing.
• Added: Command line options : show options, debug mode, timer mode, load config file, set language