From the LightUp site:
LightUp for SketchUp is a SketchUp plugin that adds realistic, realtime lighting to your sketchup models.If you would like to try LightUp yourself, visit the LightUp site for a free 30-day trial, and also the LightUp forum for announcements and support.
Add lights, add windows, and watch your SketchUp scenes glow with gorgeous reflected light, soft shadows, subtle shading. Gone are the flat, boring surfaces of old. When you're ready, you can export you lit model to a compress file containing your Model, textures and Scenes and share it with others using the free LightUp Player or LightUp Web Player.
The new release of LightUp (v2.3) is now available, in demo and retail form.