For Asus EeePCs there is a kernel module called eeepc_laptop which, among other things, makes the Fn keys work. I do not know if it works for non-eeepc netbooks, or whether or not there are other modules for other types of netbooks. On the Asus netbooks (And, I believe, most laptops) the Fn keys generate ACPI events. You might be able to use acpid to run custom commands on those events, which is something that you can find instructions on how to do with Google.
It's been a long time since I did anything fancy with acpid, it's changed a lot since then, and I never understood ACPI very well in the first place, but I hope that helps.
Last edited by -Thomas-; 01-12-2013 at 03:50 PM.