Many wireless-N routers are dual-radio, and many of these can be configured to use the second radio as a separate wireless network that is "public" and is prevented, within the router itself, from seeing the private and protected network.
If your wireless router is dual radio, see if it has this feature built in.
Another way is to buy a second wireless router and leave DHCP running on both the routers using different IP ranges. Daisy-chain the routers and set up security on the second router for your private network. Those visitor clients connecting to the first router will not be able to see the devices connected to the second router and all communication between your personal devices on the "home" network will stay on the second router and only internet communication will be sent up, through the first router, to the modem. The first router will then act as a gateway to the second one.