Peer-to-peer networking is a pretty cost-effective way to hook up a few computers and share resources such as printers and files. What's more, there are products that allow you to connect computers running different operating systems together into the same peer environment. For example, we've already discussed Samba as a possibility for including Linux computers in a Windows workgroup.
Remember, however, that peer networks are meant to be kept small before you start to develop grandiose plans for connecting a number of different operating systems into some giant peer-to-peer network. If you have more than 5 to 10 clients , network performance will suffer greatly, as will individual computer performance, as all those peers begin to access resources on the various computers.
Therefore, if you find you need to connect computers running various operating systems and think your network might grow in the future, you're better off buying a server and a network operating system that will support the different client types and provide you with the ability to centrally manage the network.