The following is a list of my favorite SketchUp photorealistic rendering plugins.
Podium (windows / mac)
Make TRUE photo-realistic rendering of your Google SketchUp models without the frustration of learning a complex program. SU Podium V2 brings high quality raytracing and global illumination with ease and at a low cost. Learn more at suplugins.com
Shaderlight (windows)
Simple to learn, easy to use, Shaderlight lets you see your image develop as you work. For rendering experts & 3D novices, it's never been easier to transform your SketchUp model in to a photorealistic render. Learn more at artvps.com
V-Ray for SketchUp (windows / mac)
SketchUp users in all fields depend on V-Ray as a quick, easy and cost-efficient way to render their most cutting-edge images. Developed with the Chaos Group, V-Ray for SketchUp works with Google’s SketchUp, one of the most popular 3D modeling tools available today. Learn more at asgvis.com
Get a full list of SketchUp Plugins at sketchup.google.com