I'm using a RPi with an Edimax usb wireless controller to bridge the home wireless network into a switch with some kit connected that I would rather not cable up to. Once you've got the wireless set up (using the wpa_gui or any number of cli variants the rest is nice and easy – if you install bridge-utils ! For reference:
apt-get update apt-get install bridge-utils
Then I just replaced my /etc/network/interfaces with something like this – I'm fixing the PI's address on the LAN so that I can get to it.
auto lo iface lo inet loopback iface eth0 inet manual allow-hotplug wlan0 iface wlan0 inet manual auto br0 iface br0 inet static address 192.168.16.100 netmask 255.255.255.0 gateway 192.168.16.254 bridge_ports wlan0 eth0 bridge_stp off bridge_maxwait 5 wpa-iface wlan0 wpa-bridge br0 wpa-conf /etc/wpa_supplicant/wpa_supplicant.conf
And thats it !! I can then add devices to the wired side of the PI and as far as the network is concerned they're directly connected.