We recently did this with two PCs and one laptop in our home. We used a wireless PCI adapter. You must have a desktop computer with an available 32-bit PCI slot, at least a 300 MHz processor and 32 MB of memory, an 802.11b Access Point (for Infrastucture Mode) or another 802.11b wireless adapter (for Ad-Hoc; Peer-to-Peer networking mode.) I specifically used a D-Link product....DWL-520 802.11b Wireless PCI Adapter. This works with the following operating systems: Windows XP, Windows 2000, Windows Me, Windows 98SE Tech support is : 1-877-453-5465 or http://support.dlink.com or email: support@dlink.com

If you're wanting to save a bit of money, a wireless network is unnecessary (though very handy, especially if you're using laptops). The most cost-effective (and physically fast) way to do it is a traditional wired network with cat-5 network cable, a few (very!) cheap 100mbit network network interface cards ("nics") and a router. The router is key, as it acts as a proxy inbetween your cable connection (the greater internet) and your little internal network, sorting out which PC requested which data and sending it the right way. Most routers designed to be placed inbetween a cable modem and a home network include firewalls as well - something very useful to look out for. No prying eyes wanted now in our little intranet :) A good selection of manufacturers to start looking at are Linksys and D-Link - they both make some nice bits of kit. The routers will typically either come with instructions on how to plug the router into the cable modem, and many will auto-setup when you do plug them in for the first time. There should also be instructions on how to configure your PC to access the routers' configuration pages (if it includes an internal admin web interface, which many do now). The way this works in terms of networking is the router gives out internal addresses to all the computers connected to it via the home network on a dynamic basis, which can't be seen individually from the Internet, and these all share the one net connection that the router has. The router acts like it's the computer in effect, sending and receiving all the data - other computers see the router as another computer. The router will (for the most part) work without much further configuration needed (though sometimes things like port forwarding may come into play) - this would be required for a wireless network too, so it's no more difficult at the end of the day, just a little subtle cabling needed (or if you're like me, the cabling as prominent as possible throughout the house, and all the cable in as gaudy a colour as possible to advertise my insane geekiness to all that are unlucky enough to be invited round to my abode). There's also many, MANY guides and tutorials on how to setup networks, of varying difficulty levels both to read and implement, so the first thing I recommend you do is go out there and get reading! Get Googling... Read up on different hardware solutions, different makes of router, make comparisons on what you think you'll need and prices etc, then go read up on the technical aspects of setting up a network, what's involved on the computers side of things. It's SO more useful to be clued up as to what's involved than to just go straight for it and buy a bunch of bits and pieces, then spend the next week sorting it all out and trying to bodge together something... And it's a big morale booster when you put together something like a network, and it works great - here's something you did yourself, instead of getting somebody else (and possibly paying em too) to do it for you.

If you have an old/slow machine with two NICs and nothing much to do with it, you could install m0n0wall, smoothwall, or astaro on it to make a free kickbutt router/gateway/firewall. Then all you need is a switch between it and all your machines.