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
There is a great post on using PowerShell and TagLibSharp on Joel "Jaykul" Bennet's site. You could use TagLibSharp to read the metatdata with any .NET based language, but PowerShell is quite appropriate for what you are trying to do.
@Thomas Owens PowerShell is now part of the Common Engineering Criteria (as of Microsoft's 2009 Product Line) and starting with Serve 2008 is included as a feature. It stands as much of a chance to be installed as Python or Ruby. You also mentioned that you were willing to go to C#, which could use TagLibSharp. Or you could use IronPython...
@Thomas Owens TagLibSharp is a nice library to use. I always lean to PowerShell first, one to promote the language, and two because it is spreading fast in the Microsoft domain. I have nothing against using other languages, I just lean towards what I know and like. :) Good luck with your project.
Further to Anon's answer - exiftool is very powerful and supports a huge range of file types, not just images, but video, audio and numerous document formats.
A Ruby interface for exiftool is available in the form of the mini_exiftool gem
see http://miniexiftool.rubyforge.org/
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).