There may be reasons for you to get a router, if you don't have one already, but you have to think about it before...
you recommend plunking down some dollars for a new piece of hardware. You may not need it.
Routers, intelligent switches that use algorithms, tables, and other means to route traffic down different pathways, often provide physical and protocol isolation, similar to a proxy server. If you need those kinds of functions, it may be that you need a router for your network.
Still, not every network really can use a router. Small LANs are usually better served with a hub or switch-based solution for file and print. But even small networks can use a router if they are connected to the Internet, if they have a remote location, or if they need specific network-management and -security features.
Routers become particularly important as your LAN grows and network collisions become more of a problem. You'll find that not only can routers help solve this problem, but they also segment your network, allowing an administrator to delegate authority for any segment that can be identified with a group or identity -- as would be the case for a branch or remote office on a WAN or the Internet.
Routers also give you the chance to filter network traffic, so routers often are part of any well designed hardware firewall solution. The prices of routers have come down considerably, and so you'll find a wide variety of routers ranging from very inexpensive small LAN solutions, to wireless routers, up to rack mounted expandable routers that can be part of a major data center deployment.
But that doesn't mean you have to run out and buy one. You can turn most servers running networked operating systems into routers. For example, Sun servers were popular as routers on the Internet before Cisco came along and build special purpose devices specifically for routing.
Barrie Sosinsky is president of consulting company Sosinsky and Associates (Medfield MA). He has written extensively on a variety of computer topics. His company specializes in custom software (database and Web related), training and technical documentation.