via @EdenExposito, Video Copilot has a new After Effects tutorial video, Light Glow:
"In this quick motion graphics tutorials we’ll create a natural light glow illuminating from your title onto a 3D surface. This tutorial also includes tips for generating a simple chromatic glow effect."
Update: Andrew added Light Particles Project to "recreate the effect with particles instead. The idea is having bright glowing particles that emit light onto the surface as they hit without having to hand animate the interactions. In the end, I used the shadow technique from our particle shadows tutorial using a copy of the particles from the top view to simulate the shadow, only here I used the copy as colored light."