here http://fanoush.webpark.cz/maemo/

You need to load or flash modified kernel. Then you may use blset script to set the brightness from shell. You can even put it to some startup script to set all levels to custom values.

Recently I found there may be some reason why the default lowest setting is so bright. When set below this the screen blinks when connected to charger (at least in latest firmware, never noticed before). Also the absolute lowest setting occasionally blinks too (caused by wi-fi?). It is probably harmless but might scare people so maybe they played it safe and set it to brighter level when it is not visible.