One other thing you might need to try besides port forwarding is to enable DMZ on your router. You will need to enable it for the local IP address that you are running the server on. Ex: The computer you are running the server on has a local IP address of 192.168.1.100 and you want to forward this out to the Internet, then you will want to enable DMZ on your router for 192.168.1.100.
Basically DMZ takes a given IP address and forwards it past the router's firewall out to the Internet, which usually allows people that are not on your local network to connect to that server. However, you might want to turn off DMZ while you do not have the server running as it does leave that computer forwarded out past the firewall that is there to help protect you. Here is the Wikipedia page for more info on what exactly DMZ does: http://en.wikipedia.org/wiki/DMZ_(computing
Also, if you have any other firewalls installed then you will need to configure/disable those as well to allow connections to your server.