EDIT: Updated for dapper
First of all do this:
If you want the onscreen display then also get
sudo apt-get install libasound2-dev build-essential linux-headers-$(uname -r) gcc-3.4
sudo apt-get install libxosd-dev
If you want osd:
tar zxvf fsfn-1.0.tar.gz
./configure && make && sudo make install
After installing that you can test this by doing:
./configure --disable-xosd && make && sudo make install
If you enabled osd:
You should see a bar at the bottom of your screen when using the fn keys.
Next would be the startup script. The script from the gentoo site doesn't work so I wrote my own. This just starts up fsfn.
Attached at bottom.
Make it executable and move the fsfn script to /etc/init.d/
To start it up on boot
chown root:root fsfn.txt && sudo chmod +x fsfn.txt && sudo mv fsfn.txt /etc/init.d/fsfn
If you want the osd to show up when you change volume/brightness
sudo update-rc.d fsfn defaults
click the start menu and SYSTEM>PREFERENCES>SESSIONS, click the startup tab and add
"fsfn -o" with order 50.