I am making a space shooter that utilizes this effect with cool results. I have a space mine that creates the line from my.y + 2000 to my.y - 2000, the particle uses my.streak = on and a cloudy square-shaped bitmap with an alpha channel. In the particle function I put my.x += random(10) - 5; my.y += random(10) - 5; and my.z += random(10) - 5; and the result is a cool laser beam that flickers around. I will be posting the effect in the projects section as soon as the demo is smooth.

Check particle00.wdl in the a6 templates, I think thats the script; It has some nice scripts for drawing lines with particles.