Well, after some work, I've gotten the first kinda release of what I've been working on. Right now it will not edit the MP3 tags at all, but it allows you to view the raw mp3 id3 tags. So please, do take a look, I think this is pretty cool.

In the zip file you will find :
Assests directory - This contains the CSS and Images for making it look pretty (iUi - Joe Hewitt).
gdsa.txt file - Contains my directory output for the get_dir_structure call.
id3.php file - A much more raw look into how this would look without the style sheet.
iUi.php file - The main program it's self, point the $path to your music own well formed music directory.
iUi.bat file - Allows to to make the iUi.htm file.
iUi.htm file - Allows you to view the final out put of the iUi.php file.

Dependencies: id3 is part of PECL and can be installed using the PEAR installer. To compile PHP with id3 support, download the sourcecode, put it in php-src/ext/id3 and compile PHP using --enable-id3.

This is also my half answer to 'What are you listening to now' thread. With what could you be listening to now, if you wanted to.
So, you guys should post up your own out put (the iUi.htm file) and let's see if our music choices match.

Which tags does this support? The entirity of id3v1, idv2.x, lyrics tags and so on? Or not quite all of that?

The ID3 functions are not provided by default in all installations of PHP, although they can be installed by the magic of the PEAR system.

Indeed, you do require the id3.dll, id3.so libaray. It supports mainly ID3 ver 1.0, only due to the fact that it uses so much less memory then that of anything else. You could change the type to ID3_BEST and it will read a much of the ID3 tag as is there, including lyrics and the like.