Heres how I set mine up:
Download this snapshot of the madwifi drivers:
Download this patch:
Open up terminal, there are a few packages we need to install first:
sudo apt-get install sun-java6-jdk
sudo apt-get install g++
sudo apt-get install gcc
sudo apt-get install patch
If anyof these requireyou to enter your root password, do it.
Now change to your Desktop in terminal
Unpack the snapshot downloaded earlier
tar -xvzf madwifi-ng-r2756-20071018.tar.gz
patch -p0 < madwifi-ng-0933.ar2425.20071130.i386.patch
Once that's done you need to make and install the driver
sudo make install
Finally probe the module
Reboot and your card should be working!
Keep the patched file somewhere safe, because everytimee you do something major to the system like updates etc, it drops the module and you need to mak, make install, and modprobe it everytime it disappeards!