yes you can ...
if you are gona use only 2 PCs then a switch or a hub mite be costly.
u can use 2 LAN cards on one PC (one for Youtele cable to come in and the other heading to your other PC) and one on the other to share the internet connection.
if you are using the above config. then you will have to keep the main/server PC on when you need net on the other PC.
if you are planning to expand then use a hub/switch.
let us know if you have further queries