All 79 Chicago Public Library branches have free Wi-Fi: The network is apparently live right now and the press releases don't indicate that you need a library card to use the Wi-Fi; some information resources at the libraries are restricted to patrons. The libraries already had free computer access and free Internet access, but a library card is needed to use the free computers, but guests can use computers if they present identification.
The library system uses Airespace equipment throughout, centrally managed with their WLAN console. Airespace also unwired the Seattle Public Library's shining new central edifice in downtown Seattle.
There's a public safety and government story here, too: city workers will be able to use a "secure channel" as the press release puts it--most likely a VLAN using 802.1X or WPA--to connect to city resources while on the road. This turns libraries into city branch offices, which must be useful in a metropolitan area.