mmv (moves multiple files based on a simple pattern replacement language). Example:

    mmv "*.mp3" "old_#1.mp3"

prefixes all files in the current directory ending with .mp3 with 'old_'. Btw., the quotes around the arguments are necesssary because mmv uses some of the same metacharacters as the shell does.

Multiple substitutions are allowed, e.g.:

    $ mmv "*.*" "#1___#2"

renames blub.xyz to blub___xyz.