What are some great rendering extensions for SketchUp?

Here’s a list of those that play nice with SU
SketchUp Sage Site > Resources > Renderers

3D Basecamp 2012 - Rendering RoundUp

My favorites:
Kerkythea is a “simply powerful” free renderer.

Thea Render is a “state-of-the-art” commercial renderer.

Both from Solid Iris Technologies