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I would recommend the Cisco Aironet 1231 with which we've had great success. Details on setting up dual SSID's for a guest network can be found here:
You will find that Netgear, D-Link, and other vendors have far less detailed explanations of what's going on under the hood, and far fewer configuration options for corporations because their cheaper products are geared towards the consumer, not the corporation. Their product offerings are therefore less complete and not optimized for security and overreaching policy goals.
It depends on which wifi router you have - some of the cheaper ones don't support that. But if you're running a device like the Netgear WNDR3700 or the Linksys WRT600N, you can run dual SSID's - one for the corporate network, and the other for Private - which will be broadcast over the 2 different frequencies(2.4ghz and 5ghz).