You could "bind" the directory to multiple mount points.
For example, if you have directory X full of cool files, which you also want available in directories Y and Z, you could do the following commands.
su mount --bind X Y mount --bind X Z
If you use sudo, you would do.
sudo mount --bind X Y sudo mount --bind X Z
It's easy (and useful)!
To unmount the directories, simply do.
su umount Y umount Z
Or if you use sudo.
sudo umount Y sudo umount Z