Just discovered how to do it on apache, just use DirectoryIndex
<Directory "C:/mydlldir/"> Options FollowSymLinks ExecCGI AllowOverride None Order allow,deny Allow from all DirectoryIndex mydll.dll </Directory> Alias /myapp "C:/mydlldir"
Navigating to http://myserver.com/myapp will load the dll, hiding the extension in the url.
You should be able to set the directory index file specifically in IIS too, of course.