Let's say you want to serve an ISO image of Red Hat 9 over a network so that others can mount and use it. To accomplish this goal, do the following:

1. mkdir -p /var/iso/redhat

2. dd if=/dev/cdrom of=/var/iso/redhat1.iso

3. mount -o loop /var/iso/redhat1.iso /var/iso/redhat

4. Now serve the ISO via HTTP, FTP, NFS, or Samba.

Of course, all of the above is assuming you have an ISO image to serve in the first place. If you don't know how, find out how to Make an ISO Image.