der_ton wrote a very useful md5 exporter for Blender sometime ago, but it wasn't as user-friendly as it could have been and didn't automatically purge not animated bones from the md5anim file which resulted in bloated files and bugs in DarkWar. I've written a blog entry about it a few months ago, you can find it here.
The script source can be found at http://svn.icculus.org/darkwar/trunk/base/scripts/ and here, if you want to download it directly.