Finally, IP forwarding works.

It's hard to find a good tutorial for IP forwarding even using my favorite search-engine google. No tutorial to discuss the intricacies of IP forwarding, just do this or do that. I think I found one good site, http://www.faqs.org/docs/iptables/, authored by Oskar Andreasson. It's a good read. I also found a more application-type tutorial but I forgot the site. Anyway, to give credit to the site owner, I'll try to llok it up and post it here later. Again.
Up next for me is Double NATing.