To hook two computers up through ethernet without a hub you will need a special cable called a crossover cable. If you use a hub then normal cables will do. You can share a dialup connection with ICS by putting a NIC in the computer connected to the dial up modem and a NIC in the other computer. ICS is only enabled on the host computer(the one connected to the modem). Everytime you need to connect to the internet, you will have to go to the host computer and dial-in (you might be able to have this done automatically, not sure though). You only have a limited amount of bandwidth, so this is split between all computers connected.
If you have more questions, this might get more responses over in networking.