In my free time I've been toying with MPQ files, working towards a stormless file extractor. I've put my work here:
http://bnubot.googlecode.com/svn/trunk/BNUBot/src/net/bnubot/util/mpq/
Nice, I've been working on it too! :) I haven't committed any of it to my SVN yet, but I'm up to the point where I need to implement pkzip and zlib (at lease explode). Good times!
I borrowed explode() from Volker Schönefeld's code (https://publicsvn.volcore.net/java/vfs/trunk/src/net/volcore/vfs/compression/Explode.java) so I wouldn't have to port it.
It would appear that zlib inflate is also supported by storm.dll, but I haven't run across an MPQ that uses it. Perhaps that's only in WoW? In any case, if I do run across the problem, java.util.zip.Inflater should be able to do the work.
Nevermind; I just went to extract a patch file, and discovered some zlib deflated files.