Do the steps one line at a time.

sudo apt-get install build-essential

wget http://bu3sch.de/b43/fwcutter/b43-fwcutter-011.tar.bz2

tar xjf b43-fwcutter-011.tar.bz2

cd b43-fwcutter-011

make

cd

export FIRMWARE_INSTALL_DIR=”/lib/firmware”

wget http://downloads.openwrt.org/sources/broadcom-wl-4.80.53.0.tar.bz2

tar xjf broadcom-wl-4.80.53.0.tar.bz2

cd broadcom-wl-4.80.53.0/kmod

sudo ../../b43-fwcutter-011/b43-fwcutter -w /lib/firmware wl_apsta.o

Then restart your computer, and it should work fine. You might have to put in your wireless network password.

via Ubuntu Forums

Step 1: All BCM43xx – Install NDISWrapper and Blacklist Native Driver

echo 'blacklist bcm43xx' | sudo tee -a /etc/modprobe.d/blacklist
sudo apt-get install ndiswrapper-utils-1.9
mkdir ~/bcm43xx; cd ~/bcm43xx

Step 2: Download and Extract Drivers

sudo apt-get install cabextract
wget ftp://ftp.compaq.com/pub/softpaq/sp34001-34500/sp34152.exe
cabextract sp34152.exe

Step 3: All BCM43xx – Configure NDISWrapper (and WPA Supplicant)

sudo ndiswrapper -i bcmwl5.inf
ndiswrapper -l
sudo depmod -a
sudo modprobe ndiswrapper
sudo cp /etc/network/interfaces /etc/network/interfaces.orig
echo -e 'auto lo\niface lo inet loopback\n' | sudo tee /etc/network/interfaces
sudo ndiswrapper -m
echo 'ndiswrapper' | sudo tee -a /etc/modules
echo 'ENABLED=0' | sudo tee -a /etc/default/wpasupplicant

Step 4: REBOOT

After your laptop is all booted up you should now be able to find wireless networks in Ubuntu 7.10, and connect to them.

If you would like, you can now cleanup unneeded files:

rm -Rf ~/bcm43xx

via Ubuntu Documentation