Right now, I\'m particularly interested in reading the data from MP3 files (ID3 tags?), but the more it can do (eg EXIF from images?) the better without compromising the ID3
use exiftool (it supports ID3 too). written in perl, but can also be used from the command line. it has a compiled windows and mac version.
it is light-years ahead of any other metadata tool, supporting almost all known audio, video and image files, supports writing (not just reading), and knows about all the custom/extended tags used by software (such as photoshop) and hardware (many camera manufacturers).