You can also use func_buttons
you know in hl, when you press a button, the button lights up?
well this is the same story, all you have to do change the textures name (you should use custom made textures
) into +0xxxxx and +1xxxxx
in the normal hl textures there are a couple of light textures wat on and off states to. You always have to start with the light off texture.
For the tut:
http://members.lycos.co.uk/EditHalfLife/tutorials/tex_light.htm