The Zigbee Alliance has been in the news recently and there has been some buzz amongst home automation groups, but it's still pretty unknown for many people. If you want a nice introduction to what exactly it is and how it plans to change the landscape for home automation, this guest post at Cocoontech seems to do a great job.
{joomsay link=http://www.cocoontech.com/portal/articles/guides/home-automation/144-zigbee-101 [CocoonTech]}ZigBee is a wireless standard and technology whose goal it is to provide low-speed connectivity (250Kbps max.) with a range of 150 feet and running from a single battery for several years. ZigBee also incorporates mesh technology so range can be extended, and over 64,000 devices can be incorporated into a network. ZigBee operates at 2.400–2.484 GHz, 902-928 MHz and 868.0–868.6 MHz. Overall, ZigBee is a much broader technology than Wi-Fi, since ZigBee can be a simple radio, a mesh transport network, and/or it can specify how applications communicate. Wi-Fi is just a transport of TCP/IP.C{/joomsay}