Extremely simple and lightweight alternative to xbacklight that uses /sys/class/backlight/... (Linux 2.6+ ONLY)
# xbright [+-=[0-N]]
NOTE: N depends on the GPU and may vary. On my machine the range is 0-15, but I've seen the range 0-255 on machines with different GPU makes.
The program is auto-configured during make
make && sudo make install
sudo make uninstall