Once you have gotten your NICs for your computers, then you need to determine what you want to use to connect all of them together. Now there are switches and hubs. Both of them will work, but for a home network, you do NOT want the expense of a switch. Not unless you get a bargain on one on eBay. A simple hub is sufficient for a home network. You can pick up a 10baseT hub very cheaply on eBay, or at the store, or online mail order. Unless you just want the expense and speed, a cheap 10baseT network will be plenty for you to share the internet and network your house. Do yourself a favor when looking for a hub. Figure out the maximum number of computers you think you will ever want to have running at your house, and then add a couple to that number. What good is a network without a couple of free hub ports open for your friends to come over and plug into your network?
Now switches are excellent pieces of equipment. They allow you to segment your network and do all kinds of fancy network management activities like monitoring traffic, monitoring ports for transmission errrors, etc. But, they are sometimes difficult to install and configure, depending on the brand and the style. For a home network, unless you are a network engineer, or have a definite reason for a switch, get yourself a hub. They are very easy to set up. Just plug in the power, then plug in your cat5 patch cables from your machines, and you are set up and running.