Vendors have begun to enable this on their routers in a variety of ways. Belkin, for example, has an option it calls "Hotel-style," meaning that users are directed to a Web landing page where they enter a special guest password. Other vendors make it easy to set up separate wireless networks just for guests. (If you use Apple's AirPort Express, on the other hand, you're out of luck -- there isn't any guest access.)
Best available routers: The USB key that you can create with Cisco's Valet can help here as well. You need to run an automated setup routine from the USB key (rather than from the Web UI) on each of your guest computers. Once you do, it will set up a separate wireless network with a different name and password that only allows Internet access.
5. Determining who is on your wireless network
The problem: Just because you think your network is secure doesn't mean that it is. It's probably a good idea to regularly check to see who is using your router -- especially if you haven't changed your router's default password. However, in a world where it's hard enough to remember to back up your computer, it's unlikely that most of us have the time or inclination to regularly check who has been on our networks.
And even if we want to, it's not always easy. Typically, most router Web UIs indicate who is currently connected, but finding this out requires digging through many menus. Sometimes the vendors hide this information under a title like "DHCP client list" and/or give you just the IP addresses and host names of current connections.
Wouldn't it be helpful if your router notified you every time someone connected? Even better, how about a historical view that shows you when and who connected to your network over the last week?
Possible solutions: There are lots of enterprise-class wireless monitoring tools, such as AirMagnet, but, price-wise, these are typically out of the reach of home and SMB users.
Check out the screens that are usually labeled "Attached devices" or "DHCP client list" to see who is connected and using which IP addresses. Some companies, such as Buffalo, clearly show how various clients have connected and what wireless devices they are using.
Best available routers: When Cisco bought the company Pure Networks, it acquired a piece of software called Network Magic. The Windows version of Network Magic will show you a pretty map along with a more useful network histogram timeline revealing who has connected when.
For some reason, Cisco includes this software in some of its Linksys routers but not the Valet M10 series. You can purchase a license for up to three PCs for $24 that will work with any router. (The Mac version doesn't have the maps or histograms.)