Here you can find the last versions of the Blitz3D exporter for Blender I developed back in 2009, since I'm not in games development anymore it won't be updated anymore; it's here just for archival purposes.
It works with Blender < 2.50; maybe you can find a modded version for Blender > 2.50 here: http://www.blitzbasic.com/Community/posts.php?topic=100592 (I'm not responsible for this version and I haven't tested it, either).