Good places to start reading:
I have a third generation MacBook. Obviously these notes are based on that but some of the stuff is relevant for other models too.
At the moment FreeBSD 7.0-STABLE is the best choice unless you want to run 8.0-CURRENT (I don't).
Among other fixes the msk(4) driver has been updated to detect the wired NIC in the MacBook since 7.0-RELEASE.
To get the wireless NIC working you have to use NDIS. Since the OSX CD contains a Windows driver the obvious thing to do is using that.
I used a Windows installation inside QEMU to get to the driver. You need to install the bootcamp drivers and then afterwards do a search for "BCM43" in order to find the .sys and .inf files.
Use ndisgen(8) to generate a kernel module that you can load.
At this time this patch to if_ndis.c is needed in order to scan and associate automatically.
There is a backlight driver outside the main FreeBSD tree. With the latest intel driver for xorg this driver should no longer be neccesary.
I have not yet tested the backlight stuff in xorg.