Animal Crossing: City Folk's WiFi capabilities will allow players to exchange letters and pictures, bid on (and sell) items at a special in-game auction site, and check out the status of other players at the Happy Room Academy. There's also an option to slap a mask of your Mii on your avatar, and a bigger city area to scope around. But it's the "community microphone" feature -- known as "WiiSpeak" -- that will really grab headlines.
[Update 1: First screens in our gallery below]
[Update 2: Nintendo reckons we can expect this in the U.S. on November 16th! (thanks, Alvin)]