You don't need any special software to set up a basic network.
All you will need is a router. Will these be wired or wireless?
Depending on your budget, there are many, many choices out there.
If you know you will only have wired connections, you can save money and go with something like this:
There are a lot of different models, but we have about 60 of these in service at my work, and they have proven to be dependable.
Having said that, I would probably go with a wireless router for more flexibility. I usually recommend this one:http://www.newegg.com/Product/Produc...82E16833122326
The WNDR line of Netgear wireless routers are all very good.
It really depends on your budget. Decent wireless routers can be had for less than $50-$75.
Once you get one, the only thing you'll need is some of these:
The Belkin's are reasonably priced, and deliver good performance. You can get them in lengths from 3' to 100' (just don't go over 100m). You'll need one for each non-wireless PC you want to connect.
Setting up the wireless takes a couple of extra steps, but is pretty easy to accomplish.
If you give us more specifics on how you want to set everything up, we can give a little more detail.
Just my 2c worth...hope it helps,