Thus far, this proceedure has worked for both a HP Compaq nx9600 and a Dell Latitude x300. Both of these are laptops with built in Broadcom wireless. They are both running Scientific Linux 4.2, kernel 2.6.9-22.0.2.EL and 2.6.9-22.0.2.ELsmp.
Here is the lspci wireless output from both the HP, and the Dell.
Dell Latitude x300
02:04.0 Network controller: Broadcom Corporation BCM4309 802.11a/b/g (rev 02)
HP Compaq nx9600
0b:03.0 Network controller: Broadcom Corporation BCM4318 [AirForce One 54g] 802.11g Wireless LAN Controller (rev 02)

1. yum --enablerepo=sl-contrib install ndiswrapper kernel-module-ndiswrapper-2.6.9-22.0.2.EL
   This gave me
   ndiswrapper-1.5-0.SL.1
   kernel-module-ndiswrapper-2.6.9-22.0.2.EL-1.5-0.SL.1
2. Downloaded the latest driver from the laptop manufacturerer. I just went to the manufacturer's support pages, and downloaded their latest windows xp driver.
3. Uncompressed the windows driver. Now you could do this by installing the driver on your windows machine. I did it by installing the drivers using Wine. I believe both of them failed on wine to actually install the drivers, but it uncompressed them just fine.
4. Copy the driver directory that has the bcmwl5.inf driver in it, over to the laptop that has the wireless card. I copied them over into a directory called /ndis/broad/ but it doesn't really matter where, but for this example, I'll use /ndis/broad/
5. ndiswrapper -i /ndis/broad/bcmwl5.inf
6. ndiswrapper -l
   This should show something like

     # ndiswrapper -l
        Installed ndis drivers:
        bcmwl5          driver present, hardware present 

   
   Note: If is says something like the driver doesn't work, then do a 'ndiswrapper -e bcmw15', and a 'ndiswrapper -i /ndis/broad/bcmwl5a.inf' to use the other driver that is in the directory.
   Note2: If it says 'driver present' but not 'hardware present', then ndiswrapper knows how to use the driver, but the driver doesn't match your hardware.
7. modprobe ndiswrapper
   Which should load the driver.
8. ndiswrapper -m
   Which put's the correct syntax into your modprobe.conf area, setting things up a wlan0
9. Setup your networking as you would any other wireless card. It should be setup as wlan0

Extra Notes

The BCM4318 (HP nx9600) will only do 'encrypted' wireless connections. I haven't been able to track this down. It works just fine when you have to put in an ESSID and a password, but when you try to connect to a network that isn't encrypted, and just let's you connect to it, it refuses.
I've tried everything I can think of, complete down to the exact same network settings on a wireless machine that was working, and tried on several different open wireless networks.

Just for fun (and to try and fix the above 'unencrypted' problem) I tried using the broadcom driver from the Dell on the HP (from the BCM4309 on the BCM4318). The driver loaded but I would get a 'driver present' but not a 'hardware present'.