If you've seen those laser cutting guides on miter saws and wonder if you can add one to your old saw, take heart. It's possible, and not terribly expensive. The guide fits alongside the blade, replacing the outer washer. When the saw starts running, the guide shoots a laser beam that shows exactly where the blade will cut.
Quarton makes a product called the Infiniter Laser Cutting Guide, which fits on most miter saws and circular saws. Three small replaceable alkaline batteries provide the power. The centrifugal force of the saw blade automatically starts the laser, so you see the beam as soon as you pull the trigger. Rockler sells the guide (rockler.com; check the Web site to make sure the guide will work for your saw). I installed it on my miter saw in less than five minutes. The blade cut exactly on the laser mark.