Well if you only want a network, without internet across these computers... switches would work great.
If you would like an internet connection, then atleast 1 router will be required.. (or an always on computers with 2 ethernet cards)
HUB: A simple way of splitting an internet connection, and create a network.
The hub is simple because they way it relays information to all the PCs connected. The hub sends all information to all pcs if the pc requested it or not.
Switch: A smart hub, as it does the same as a hub, yet only sends relavent information to relavent PCs.
Router: A router is basically a switch with a feature to connect to an isp for an internet connect. It will also usually have other features like firewalls...
A switch would only be REQUIRED when a network exceeds a certain number of pcs. I would say 5-8 computers on ONLY HUBS would be bad. If all these machines are running at the same time, they are all being bombarded with the same info, thus slowing each connection down.
What you need: You would get a router (if you plan on having an internet connection to all PCs). You would need the relavent CAT5 cable to wire through the walls, and the external female jack for the walls. NOTE: Cat5 cable can be purchased by the roll, and spliced for your desired length.
Also 1 ethernet card in each pc. I would recomend buying a router with the the number of computers you plan on running +2, and an option for wireless. I would say 60-70$ (US) for a good router.
The hardest part of the setup would be running the cable through the walls.
Good luck
