Since there seems to be anti-switch sentiment, I've edited my original reply to a more conventional broadband router. Still nice and cheap.

It's worth noting that if you use on PC to host the internet connection for another, you need to be aware of a couple of things. (1) The hosting PC will need two ethernet ports, and (2) the hosting PC will need to be on whenever you hope to connect the other PC to the internet.

For reasons of electrical bills alone, I'd recommend spending the $50 or so for a hardware solution. Assuming, of course, that you're looking to share an internet connection.