I have written two illustrated articles on how I made a fixed positioning laser on the Avid CNC spindle motor of our machine. This laser is now available anytime, and is helpful for positioning and measuring on the machine.
These were posted on my blog for the general public, but are specifically of interest to other Avid CNC machine owners.
I used a pair of laser line generators built into my dust boot base. They can be independently adjusted so that the align to the axis of the spindle. They are off to the side far enough so they cross at the center at any spindle height, with or without a bit in the collet.
I thought they would be more useful, but in the end I just end up using the bit to allign with things. its just as easy.
One thing I liked it for was flying across the the table and jogging to a position over the workpiece where I wanted to manually set X and Y zero, or align to be over the touchplate without having to drop Z down 8 or more inches just to see if it lines up.
I have a switch to toggle between the crosshairs and the halo light that is around the spindle.