I just installed Raspbian Wheezy (2014-01-07-wheezy-raspbian.img) on my Raspberry Pi, connected it to my AirPort with an ethernet cable and booted it with this wifi dongle (Sitecom N300) inserted:
As you can see from the output of lsusb and dmesg, this dongle is using the RTL8191S chipset, which, as I'm told, should be supported in this version of Raspbian. However, there's no wlan* entry in iwconfig's output:
pi@raspberrypi ~ $ iwconfig lo no wireless extensions. eth0 no wireless extensions.
firmware-realtek was already installed, so what am I missing?