I have the following wireless hardware on a Compaq evo N600c laptop running lubuntu latest.

ciaran@compaq:~$ lspci -vvnn | grep 14e4
03:00.0 Network controller [0280]: Broadcom Corporation BCM4306 802.11b/g Wireless LAN Controller [14e4:4320] (rev 03)

Following the instructions from here :

http://www.linuxwireless.org/en/users/Drivers/b43#b43_and_b43legacy

I opted for the legacy firmware installer, following instructions for internet install to the letter (with no errors). i.e. I successfully installed

sudo apt-get install firmware-b43legacy-installer 

In the nm-applet I now get

Wireless networks device not ready (firmware missing)

I open up Additional Drivers, but the list is empty. I have commented out this line in /etc/modprobe.d/blacklist.conf

#blacklist bcm43xx

Contents of firmware dir:

ciaran@compaq:/etc/modprobe.d$ sudo ls /lib/firmware/b43legacy/
[sudo] password for ciaran: 
a0g0bsinitvals2.fw  a0g0initvals5.fw    b0g0bsinitvals2.fw  b0g0initvals5.fw  ucode11.fw  ucode5.fw
a0g0bsinitvals5.fw  a0g1bsinitvals5.fw  b0g0bsinitvals5.fw  pcm4.fw       ucode2.fw
a0g0initvals2.fw    a0g1initvals5.fw    b0g0initvals2.fw    pcm5.fw       ucode4.fw

Edit:

from dmesg:

[ 4460.193382] b43-phy0 ERROR: Firmware file "b43/ucode5.fw" not found
[ 4460.193393] b43-phy0 ERROR: Firmware file "b43-open/ucode5.fw" not found
[ 4460.193401] b43-phy0 ERROR: You must go to     http://wireless.kernel.org/en/users/Drivers/b43#devicefirmware and download the correct firmware for this driver version. Please carefully read all instructions on this website.

Yours in hope.