If you edit the file bootlocal.sh, you can add commands there and they will run automatically as root on boot. If you have backup/restore enabled, the changes to bootlocal.sh will be saved automatically.
If you're not comfortable using vi from the command line, you can load the beaver extension to edit bootlocal.sh. As an example, to load the module named "b43", add the line "modprobe b43" to bootlocal.sh - without the quotes ""