Brief description of TagLib:
TagLib is a library for reading and editing the meta-data of several popular audio formats. Currently it supports both ID3v1 and ID3v2 for MP3 files, Ogg Vorbis comments and ID3 tags and Vorbis comments in FLAC files as well as MPC.
TagLib is distributed under the GNU Lesser General Public License (i.e. LGPL). Essentially that means that it may be used in proprietary applications, but if TagLib itself is disributed then the sources (for TagLib, not the application using it) must be included in the distribution medium.
TagLib homepage: http://developer.kde.org/~wheeler/TagLib.html
I didn't find any "official" port of TagLib but I googled up some modified source files (author unknown) which did make TagLib compile under Win32 using MSVC, but the library was unstable and had some other errors. So I copypasted most Win32-related macros from the port and spent a day making it work for me.
Here's the list of bigfixes and modifications I made:
Note 1: The port has been tested with embedding ID3v1 and ID3v2 tags only so far.
Note 2 (added 2009/07): Since version 1.5, TagLib officially supports Windows, but I didn't check if it is GCC or MSVC and whether it uses my patch or not. You might be interested in trying the newer official version first.
The library is distributed under terms of GNU Lesser General Public License 2.1 or higher, at your option.
taglib-1.4-with-Win32-port-by-SG-20080102.tar.bz2 (331 Kb) [4679 d/l] - source code.