Hi,
don't know which router you are using, perhaps one of those with a webfrontend to setup ? Or a linux/ *BSD box ?
If you're running one of those with webconfiguration you should have a manual that explains how to setup this thing
To get your webserver running, setup apache on a box of your choice and redirect port 80 (tcp) from the routers WAN address to port 80 on the machine where apache is running. If you also want to use secure-http then you need to redirect port 443 tcp/udp too.
All other services and ports can be found in /etc/services, at least the first 1024, well known, ports.
If you're running a linux box check out the ipchains (kernel 2.2) or iptables (2.4) howto. it's great
cu
p.s.: if you got one of those cisco boxes, go and buy another router
