Sharing Internet Connection
Solution 1:
A common approach is to get a wifi or ethernet router.
Connect this device to the cable internet device, then connect your computer to the wifi/ethernet router.
Take a look at http://compnetworking.about.com/cs/homenetworking/a/homenetguide.htm
Solution 2:
I recommend buying a Linksys WRT120N, this one is less than 50US$. There are other brands that are even less expensive, but I prefer Linksys.
There is one port for the connection to the cable modem, and there are 4 ports for computers (alternatively you can connect other computers via wireless)